Stefan: Cooking Thanksgiving dinner is harder than ever. Aunt Ethel just found out she's allergic to vegetable oil, cousin Sammy's a vegan, and dad doesn't trust anything that doesn't come from his own farm. You're trying to bring all these people together, and you need to feed them something. But in some ways, this mammoth-task is easier than ever because there are so many more options than there used to be.

You can replace oil with applesauce for Ethel, get some fake turkey for Sammy, and your dad? Well, he might just have to watch the first video in this compilation. Some food substitutes are natural and others are artificial, so Hank is going to get us all on the same page about what that even means.

[slide: "The Truth Behind 'Natural' and 'Artificial' Flavors"]

Hank: If somebody gives you the choice between two tasty looking snack cakes, but one is labeled "naturally flavored" and the other "artificially flavored," most people would probably go with the "natural" one. It sounds better; who wants to eat food that's fake? I like real food. But those labels can be pretty misleading. In fact, the flavorings could be chemically identical.

There are rules as to what gets labeled "natural" or "artificial," but they're pretty subtle, and you definitely don't need to avoid artificial flavors to stay healthy or be eco-friendly. The only reason you might want to opt for the natural version in some cases is its... just it's flavor.

In the US, artificial and natural flavors are defined by the Food and Drug Administration (FDA), because that's the agency that gets a say in how companies market and label their foods.

So first, the term "flavors" itself refers to ingredients that are in the food mainly for their taste rather than any nutritional value. So, an apple in an apple pie would certainly be adding to the overall flavor, but it would not technically be considered a flavor or a flavoring. And the FDA considers something an natural flavor if it comes from a plant or animal. That source could be virtually anything: fruit, bark, herbs, veggies, meats - the list is long. But if it's made from a plant or an animal, it's "natural." If not, it's "artificial." It does get a little more complicated than that but in the vast majority of cases, the difference between the two is only the source.

- the source. We're sticking to the specifics of the US here, but plenty of other countries differentiate these flavors along the same lines, so you'll see similar claims on their food packaging. 

Seems simple enough, but if you think about how we experience flavor, you can see why this whole binary system the FDA has cooked up is not necessarily all that useful. Because what makes your favorite chocolate chip cookie so delicious comes down to the molecules you taste and smell, not where those molecules come from. They're chemicals whether they come from natural sources or are made from scratch in a lab. 

And in many cases, the molecules in natural and artificial flavors are exactly the same, down to the placement of each atom and bond. That's because for a lot of common flavors, we know the main chemical behind them. And whether you purify it from fruit or make it synthetically, a compound is a compound is a compound. 

Take the vanilla you might use when you bake cookies; the main flavor component of vanilla and the one that we recognize as having that sweet characteristic taste is a chemical called "vanillin." You can naturally extract it from vanilla beans by soaking them in water and alcohol, or you can make the exact same chemical in the lab. If you go the all-natural route, expect to pay big bucks though, because vanilla beans are the fruits of finicky tropical orchids; they're a huge pain to grow and harvest. And vanilla is the world's most popular flavor; we cannot grow enough beans to flavor everything we want using only the real stuff.

There is another natural way to get vanilla flavor with something called "castoreum," but that's not likely to be a fan-favorite; that's because it comes from the castor sacs of beavers, which are located down near their... tails - basically, flavoring via beaver butt. Milking beavers for their secretions is not exactly a high-volume industry either, so castoreum is too expensive to put in most foods.

But in the lab, you can make the same vanillin in huge batches and for much less money by doing some fancy chemistry on paper pulp or petroleum derivatives. That may sound less appetizing than getting it from beans, but remember - the molecule you get at the end is exactly the same.

- exactly the same. And that's how we're able to vanilla-fy most of the foods we eat. So, maybe don't write off artificial vanilla just because it's not natural; you'll save some big bucks.

Then, there are also some misconceptions about the environmental impact. Counterintuitive as it might sound, natural flavorings aren't always so great for nature; they can have much bigger environmental footprints than their artificial counterparts.

Take massoia lactone, a chemical that tastes like coconut, which you can find in the bark of certain trees in southeast Asia. The tricky part is if you strip the bark to get it, you kill the tree. So, as much as we want to have that lovely piña colada flavor, the natural version is really inefficient and unsustainable. Whereas synthetic chemists can whip up massoia lactone in the lab, no tree-stripping necessary.

Granted, artificial flavorings aren't perfect for the planet either. They're often made from oil and can require special materials that aren't environmentally-friendly. Production can also create wastewater. Still, that's usually better than killing entire groves of trees or going through thousands of kilos of fruit in search of specific flavor compounds.

There is one major downside in keeping things strictly in the lab though - the taste. Because while synthetic vanillin is the same molecule you'll find in the stuff from vanilla beans, real vanilla has hundreds of other compounds that subtly change the flavor. Artificial vanilla is a pretty good substitute because around 80% of vanilla flavor comes from that one vanillin compound; most people can't tell the difference. But other flavors are much harder to replicate.

Artificial strawberry might be delicious, for example, but if you think about it, it doesn't really taste like strawberries. That's because you simply can't reproduce that flavor very well with one or two chemicals - it's super complex. So, the purity you get with artificial methods may sometimes make for less sophisticated flavors. On the other hand, it also means that those flavors are better-known to scientists and more rigorously tested. If this runs counter to your intuition, you're not alone.

Packages proudly proclaiming "no artificial flavors" are trying to appeal to the common feeling that substances from Mother Nature are inherently safer and better than ones invented and produced by people.

- produced by people. That's called "the naturalistic fallacy." But nature isn't infallible, and there's all kinds of stuff out there that's natural, but will also super kill you. Just because a flavoring comes from a plant or animal doesn't mean it's safer or healthier. Which is why US flavor regulations apply to both natural and artificial flavors; it's a system called "generally recognized as safe" or GRASS.

Basically, back in the mid-20th century, the FDA decided that food-additives should be tested, although they could be exempted from review if experts already agreed that the substance was safe. Since the rules took full effect in the late 1950s, just two flavors have been banned, one natural and one artificial: Calamus, which comes from a plant known as "sweet root" and cinnamyl anthranilate - a synthetic compound that gives a grape or cherry flavor. Some flavorings have raised other types of health flags, like diacetyl, the artificial buttery flavoring in microwave popcorn. If it's inhaled in extremely large amounts, like if you work in a popcorn factory and don't use protective equipment, it can cause a lung disease known as "popcorn lung." But eating it isn't a problem, so we still use it.

In theory, it's still possible that some flavors we use have minor negative health effects we just don't known about, even with this testing system. One complication is that the evidence is summarized by an industry group [the Flavor and Extract Manufacturers Association]. But since the rules apply to both types of flavors, there's no reason to be extra suspicious of the artificial ones.

Another part of artificial flavoring's bad reputation comes from the fact that it's in processed foods, which are less healthy for you; they're often high in sugar and fat, while also being low in fiber and nutrients. But that's not the flavoring's fault. And of course, natural flavoring is used for the exact same thing. 

Perhaps the most misleading example of this is orange juice. Americans used to get most of their orange juice from concentrate, but these days, we tend to buy it in cartons where the juice doesn't need to be diluted. It seems like a fresher option, and companies have marketed it that way to get a premium price. But the juice isn't as fresh as they make it sound. Because the realities of large-scale production, the juice ends up sitting in tanks -

- in tanks for months at a time. To keep it from spoiling, producers pasteurize it and also remove all the oxygen in a process called "deaeration."

To be fair, that processing is important to keep the juice safe to drink, but it also removes a bunch of the nicer flavor compounds that make freshly-squeezed juice so refreshing. The juice might not be from concentrate, but companies still re-flavor it right before it's put in the carton with what people in the industry call "juice packs." These packs are mix of flavors - usually from oranges, orange oil, or orange essence - so technically, they have natural sources. But that doesn't mean the flavor is coming from freshly-squeezed orange juice, or that the juice is somehow less processed and healthier because the flavorings are natural. 

Once you find out what the terms "natural" and "artificial" really mean, you start to see this type of misleading marketing everywhere. But if you think it's confusing now, just wait a few years, because biotech is getting in on flavorings, blurring the lines even more. 

Companies are trying to come up with new ways to make flavors that still count as "natural" under current labeling regulations even though the source might be bacteria or yeast rather than any recognizable plant or animal. With genetic engineering, you can program microbes to produce certain flavor molecules, then isolate the molecules and use them just like other flavorings. That could be a more efficient and eco-friendly solution in some cases, especially for hard-to-source flavor compounds. But in a way, it would make the labeling claims on food packaging even more meaningless.

Like, is that "all-natural" vanilla from vanilla beans or a very special strain of yeast? If you wanted the natural stuff for a more nuanced flavor, you'd have no way of knowing what you were getting. For now, just don't be fooled by claims that sticking to natural flavors is healthier or better for the environment. Tastes and flavors are based on chemistry, and a lot of the time, the artificial ones are just as good.

[slide]

Stefan: Sometimes artificial flavors are just as good as natural ones. After all, the molecules that make them tasty can be identical in artificial and natural foods. But if you're not sold yet, the almost universal natural substitute seems to be applesauce. Here's the science -

- the science that makes applesauce the best stand-in for butter, oil, and eggs.

[slide: "Why Can Applesauce Replace Butter? And Oil? And Eggs?"

Hank: Do you ever want to indulge in some baked deliciousness without quite so many fats? Or maybe you want to cut animal products out of your cooking. Well, some bakers use applesauce to replace the butter, oil, or eggs in their favorite cake recipe. But how can the carbohydrates in applesauce replace the fats or proteins in a pastry? Baking is just chemical reactions, so we need to understand how these ingredients work together in the first place.

When flour and water come together, two of the proteins in flour - gliadin and glutenin - unravel and combine to form long strands of gluten. So, if you're making bread, you add water to the dough to start making gluten, and then keep kneading the dough until it's full of a super stretchy gluten network. All that gluten makes a nice, chewy bread.

But pastry chefs try to keep gluten at bay to get a light and airy texture in cakes and pies. How do they do that? With fats. The fats in your pastry dough are hydrophobic, meaning the butter and oil molecules don't like binding with water. These fat molecules coat the flour proteins so they don't interact as much with the water and form too much gluten. In other words, all that butter in pie crust helps it stay tender and flaky.

So, when bakers replace fats with applesauce, they're trying to achieve the same thing in a slightly different chemical way. The applesauce is full of a polysaccharide called "pectin," which normally holds cell walls together in some plants, including some fruits like apples and berries. But pectin doesn't coat the flour proteins like the fats do. Instead, it competes for the water's attention to form a jelly-like mesh of its own. That way, less water interacts with the flour molecules and less gluten is formed.

Baking with applesauce can be tricky; it has a lot of water on its own, so adding too much applesauce could also make a muffin too bready. But applesauce can replace more than just fats. It can also substitute for eggs, which generally help thicken some baked goods and give them some more texture. An uncooked egg white is basically a bunch of folded-up proteins floating in water. When you heat egg whites up, -

- whites up,  those proteins unfold and start sticking to each other, which helps keep your batter together. And when you heat up pectin, those polysaccharide molecules start binding to each other and other molecules, like water, to create a tangled, gummy network. Just think of a jam or jelly; that gelatinous texture is thanks to pectin. So applesauce can give your cake some structure just like eggs do, all while keeping it tender as well. Tasty. 

[slide]

Stefan: Structure and texture are dead giveaways that you've tampered with a recipe, and that's why the protein interactions that applesauce initiates are great for so many of your kitchen needs. I mean, sometimes even using a natural substitute makes it taste unnatural simply because you used a substitute. And if the picky eater at your Thanksgiving dinner table is just going to shove your natural substitutes to the side of their plate, artificial substitutes don't stand a chance. Unless, maybe we use tools like cellular agriculture to make artificial food substitutes as close to the real thing as possible. So, here's how we do that to make artificial meat.

[slide: "Animal-Free Animal Products With Cellular Agriculture"

Hank: Nowadays, a lot of people are looking for ways to eat less meat and other animal products because of either ethical or environmental concerns. The good news is that there's a ton of plant-based alternatives, from just straight-up plants like chickpeas to products like tofu and seitan, also known as "wheat meat." But there may actually be a way to still get animal products without having to raise and then butcher animals, like lab-grown meat, also known as "cultured meat" or "cellular agriculture." With this technology, you can make things like protein mixes and chicken nuggets, and this isn't just a potential dream for the future; some of these things are already hitting the shelves.

Firstly, let's talk about milk. Now, there are already dairy alternatives like soy milk, almond milk - there's every kind of milk now. But they don't have some of the signature proteins found in real dairy. Particularly, a macromolocule called "casein" makes up about 80% of the protein in milk. And whey, which is a mix of a couple of enzymes, makes up the other 20%. but a couple of companies are now producing -

- producing and/or selling what they're calling "animal-free dairy." 

Instead of using cows, they use transgenic microbes - microorganisms with foreign genetic instructions to make proteins. Scientists already know the amino acid sequence for casine and whey protein, so it's pretty easy to turn that into a genetic sequence and add it into a microbe, like a yeast cell. These microbes are then grown in a reactor, kind of like beer fermenting in a vat.

When the company's ready to make some milk, they filter the casein and whey proteins out of the brew, and then those are mixed with other ingredients, like fat and sugar. What you end up with is something that apparently looks a great deal like the kind of milk you would get from a cow. One company has already turned this into commercial products, like ice cream. And milk isn't the only product companies might be able to make this way; another company is using a similar process to make transgenic egg whites.

So, that's cool, but while those are definitely animal products, they are not meat. Meat is, after all, not just protein; it's traditionally, at least, actually a part of an animal - largely, the animal's muscles. But there are a number of companies that are looking for ways to grow animal's cells without needing the entire animal. In fact, the first lab-grown meat has already hit the market; in 2020, Singapore approved the sale of lab-grown chicken.

To do this, scientists take stem cells from an animal obtained by a small tissue sample. Stem calls are a kind of cell that can turn into many different types of cells, including, for our purposes, muscle cells. These cells are then allowed to grow in a solution of sugars, proteins, and other nutrients. A kind of scaffolding made of proteins may also be used to help give the cells something to grow on. When enough cells have been grown, they're harvested, and in the Singapore example, they have so far been turned into chicken nuggets, though you could conceivably turn it into other products as well.

The company in that case has said the process takes about 14 days. The taste is apparently - drum roll, please - like chicken, though the texture doesn't quite match and is closer to firm tofu than chicken.

- tofu than chicken. Texture, it turns out, is hard to pull off; that's because meat also contains things like fat, connective tissue, and capillaries and veins. But also, importantly, the muscle cells aren't just a clump. In real tissue, muscle cells are packed into long fibers - the "grain" of the meat. This kind of structure is hard to mimic; that's why a lot of the focus so far has been on things like ground meat because the texture isn't quite as important.

But researchers have been making breakthroughs. Playing around with different scaffolding designs, like long strings, has yielded some promising results. In early 2021, for example, a Japanese team announced that they had success with a method that combined both a place where the cells could grow and zapping them with electricity to make the muscle cells contract. That combination made the individual cells actually come together into the proper muscle fibers that impart so much of the texture to meat. They were using cow stem cells, and so they tested their results by cooking teeny, tiny steak strips; that technique is still small-scale, and they're only one of many different groups working on this in different ways, but they think this technique could be a way forward.

These inventions mean that we may soon see animal-free animal products on our grocery shelves that provide us ways to eat less meat without eating less meat.

[slide]

Stefan: Okay, so texture is still a struggle, but researchers are on the case. And some would argue that we've already succeeded at making artificial meat, but we haven't been so successful when it comes to other foods like salt. A younger me has an explanation for why it's so hard to make a good salt substitute.

[slide: "Why Can't We Make a Good Salt Substitute?"]

We know from chemistry that there are hundreds of salts out there. They're compounds made up of positive and negative ions, usually formed when an acid reacts with a base. But when it comes to food, there's really only one salt that gets us salivating over potato chips - sodium chloride, otherwise known as "table salt." In fact, chemists have been trying to cook up a good salt substitute for decades, and it's proven downright impossible -

- impossible; nothing quite matches the flavor of the tried and true.

So, what make sodium chloride so special? Well, the truth is scientists haven't totally figured it out yet, mostly because this seemingly simple taste is actually the one we know the least about. Still, we do know the basics, and it seems that the sodium and chloride ions that table salt gets broken down into on your wet tongue happen to be the perfect ions for a couple of our salt taste receptors.

We haven't identified which receptors recognize the anion or negatively charged ion in a salt, but generally speaking, we perceive smaller ions as saltier, which is great for table salt because chloride is relatively small. So, something like sodium acetate is far less salty because the acetate ion is much bigger, although it's sometimes used to give chips a salt and vinegar flavor. 

Since replacing chloride doesn't really work, the other option would be to replace the positive ion - sodium. Now, one of the best studied receptors is the epithelial sodium channel, which is - you might guess - specific to sodium. These pores let sodium ions flow into cells, and in taste cells, the incoming sodium ultimately sends a signal to the brain. And the channel selectively for sodium is one reason why the best salt substitute out there, potassium chloride, still isn't very good.

The potassium ion can't pass through the channel to tell your brain, "Hello. Infusion of salty flavor!" And that salt also gives off weird, bitter, metallic flavors that are hard to miss. Our tongues are so acutely sensitive to these, that companies trying to lower the sodium content of their foods this way actually have to use a mix of regular salt and potassium salt so it's less noticeable. Potassium chloride also isn't safe for people with kidney disease and can cause dangerous interactions with some drugs. So, while it can work for some people, it's not a perfect solution.

Now, there actually is a wonderful salt substitute, at least in terms of flavor; lithium chloride tastes almost exactly the same because those epithelial sodium channels also let lithium slide in. But you don't want to eat it, because it's toxic. Back in 1949, a company sold "Westsal," a lithium chloride based salt, as a nice alternative for people with high blood pressure or heart disease. But then, doctors started seeing people with lithium poisoning, and a few people even died.

Chemists are still working on more creative -

- more creative salt combinations that may one day closely approximate table salt. But until then, if you want a more salty flavor, you'll have to reach for good old sodium chloride.

[slide]

All things considered, I'd rather not have a salt substitute that's poisonous, so maybe put that one on the back burner for now. But in the meantime, we can focus on another kitchen essential -sugar. Now, we have technically made artificial sugar, but maybe we're not so good at it yet. Here's how artificial sweeteners can affect your health.

[slide: "Are Artificial Sweeteners Bad for You?"]

Recent research has painted a pretty bleak picture for sugar lovers, linking excessive sugar consumption to obesity, diabetes, and heart disease. So, you might be tempted to switch to artificial sweeteners or any of the myriad of high-intensity sweeteners available today. At first glance, that seems like it would let you have your cake and eat it, too, giving you the sweetness of sugar without so many calories. And that's about where things were in 2013 when we talked about sweeteners in our episode on the science of sweetness.

But since then, scientists have been hard at work studying the potential impacts of switching from sugar to things like Sweet'n Low or Splenda, and a fierce debate about the effect of sweeteners has emerged. One thing seems certain, though - they aren't going to fix all the things sugar broke.

Several large epidemiological studies in humans - some containing nearly half a million participants - have basically eliminated fears raised in the 1970s that artificial sweeteners, like saccharin, cause cancer. But in the past couple decades, studies have started to suggest that they and other high-intensity sweeteners might still have negative effects on the body.

Some of the strongest evidence against these sweeteners centers around the idea that they help with weight loss. They're used in things like diet sodas or low-calorie snacks because they can replace sugar's sweetness with way fewer calories. Some, like the steviol glycosides found in the natural sweetener Stevia, aren't processed in our guts the same way as sugars, so they don't have any calories of their own. Even those that do are tens to thousands of times sweeter than sugar, so they can be used to make low-calorie substitutes for our favorite sweets.

But in 2014, a large meta-analysis of randomized controlled trials - the gold-standard for health research - found that using artificial sweeteners instead of sugar resulted in weight loss of -

- in weight loss of just 0.8 kg on average. And individual results vary from tons of weight loss to weight gain. The lack of a clear weight loss benefit might come down to what sweetness does to mammal brains.

Normally, a sweet taste means that the body receives a bunch of calories, the food energy we need to survive. So, some scientists think that tasting sweetness without getting an energy boost confuses the parts of the brain that regulate hunger and fullness. This confusion could mean we don't know when to stop eating, so we actually end up eating more overall. Though this phenomenon hasn't been conclusively demonstrated in people, studies in animals suggest it can happen.

In one study, rats fed sugary food ate much less of a sweet yogurt when offered it than rats only feed saccharin-sweetened food before. And there might be other factors at play as well that explain why lowering sweet calories doesn't translate into weight loss. We used to think that because high-intensity sweeteners aren't digested like sugars they just pass through our guts unnoticed, but several recent studies in rodent models have suggested they can affect intestinal bacteria, which play a big role in how we process food.

For example, a paper published in Nature in 2014 found that mice fed saccharine developed changes in their gut microbiome and symptoms of prediabetes. Scientists then transferred gut bacteria from these mice into germ-free mice - animals that are born by caesarean section and raised in totally sterile conditions. And those mice also developed prediabetes symptoms, which is strong evidence that sweetener-induced changes to the microbes were to blame.

But similar studies haven't been conducted on people, and I know we say this a lot, but it's worth repeating: Rats aren't people. In fact, that's a common theme in sweetener research. Since, for ethical reasons, most studies on humans are observational, it's difficult to determine cause and effect. And studies finding strong negative effects on sweeteners and animal models have created a rift of sorts in the scientific community.

One camp thinks that sweeteners actually cause harm, and that the animal studies show us what's really going on; they point to observational studies in humans as further proof, like a 2017 study of over 64,000 women which found that heavy consumers of any type of artificial sweetener were about 21% more likely to develop type 2 diabetes.

The other camp says that the rodent studies aren't realistic; -

- aren't realistic; the rodents are fed way too much of a sweetener, for example. And so, those researchers think something else explains the human study findings - reverse causation. As the name implies, that's when two observed things are indeed correlated, but the cause and effect are flipped from what you think. In other words, yes, sweetener consumption is linked to diabetes, but not because the sweeteners are causing diabetes. Instead, it could be people knowing they have a higher risk for diabetes that drives their sweetener use. And that's what scientists in a 2011 study of more than 40,000 men concluded.

While there was an irrefutable link between sugary drinks and type 2 diabetes in their data, the link between diet drinks and diabetes disappeared then they corrected for other potential factors, like the participant's starting weight. The scientists in the 2017 study of women did similar statistical analyses to control for BMI and several other major risk factors for diabetes, and the connection between sweeteners and diabetes remained significant. But the statistics are very complicated, and many scientists, including those involved in the 2017 study, argue the math isn't always able to completely remove the influence of other risk factors - a concept known as "residual confounding."

For example, it's possible the significant increase in diabetes risk from sweetened drinks in the 2017 study was driven by participants that were obese at the beginning of the study. Because of the difficulties of conducting nutritional science and people, the scientific debate about high-intensity sweeteners isn't going to be resolved anytime soon. But there is something everyone seems to agree on, and that's  that high-intensity sweeteners aren't a magic bullet. So, if you really want to improve your overall health, you might want to limit both sugars and sweeteners in your diet.

[slide]

Eating a lot of sugar or artificial sugar is still eating a lot of sweet stuff either way, and when it comes to the food you put in your body, the age-old guidance holds true: Everything in moderation. Here's Michael to explain how swinging in the other direction and becoming obsessed with health can actually make you unhealthy.

[slide: "How Being Obsessed With Health Can Make You Unhealthy"]

Michael: Everyone wants to be healthy. But sometimes, in our pursuit of fitness, we take things a little too far. And that can ultimately mean a healthy behavior becomes -

- becomes an unhealthy one, and maybe even one that kills you.

Take dieting, for example. Being overweight can increase your likelihood of certain diseases and even death, so you might decide to go on a diet to be healthier. But dieting isn't always so great either. Lots of diets are based around cutting out specific foods, and axing things wholesale can mean you don't get enough of key vitamins and minerals, collectively called "micronutrients." And, in the most ironic way having micronutrient deficiencies actually makes you more likely to gain weight or develop diabetes, increasing your risk of mortality.

Trendy diets, in particular, are notorious for failing to include everything you need. For instance, a study published in 2017 showed how the paleolithic diet, which excludes all processed foods, resulted in an iodine deficiency in obese, postmenopausal women. Iodine is especially important for thyroid function, that hormone-secreting gland in your neck which helps control things like your energy level. It turned out that when the subjects went paleo, they cut out good sources of iodine, like table salt and dairy among other things.

Similarly, a 2018 study analyzed the nutrient content of the three most popular diet plans available through Amazon. They found that one week of commercial low-carb diet didn't deliver enough vitamins B1, D, and E, as well as calcium and a few electrolytes. And the vegan weight-loss plan they analyzed failed to provide enough of certain B vitamins, calcium, and vitamin D, and it was low in protein, too.

Those deficiencies, especially in calcium and B vitamins, are frequently seen when researchers compare vegans to omnivores, and they can compromise bone and muscle health as well as your immune system, making you more susceptible to infection. That's not to say that you can't be vegan and healthy, or paleo and healthy; you just have to make sure you're actually getting everything your body needs.

To avoid this whole micronutrient nightmare, you could diet by cutting the amount you eat, rather than specific foods. Eating less is arguably the most effective way to lose weight. But if you feel like you're always fighting with the scale - losing 5 kg, then getting it back, then losing it again - you could be doing more harm than just staying overweight.

While obesity is generally not great for you, weight fluctuation - also called "weight cycling" or "weight yo-yoing" - may actually be worse and carry a higher mortality risk. While there's no consensus on how much your weight has to fluctuate to count, one study out of Finland -

- study out of Finland quantified severe weight cycling as losing and gaining at least 5 kg at three different times. And this ends up being a pretty wide-spread problem, since the majority of people who do manage to lose a bunch of body fat gain it back, Then, if they diet again, the cycle repeats.

Bouts of weight loss aren't usually all that harmful unless you lose a lot of weight quickly, but repeated periods of weight gain are harmful, and they stack up over time. When your fat cells grow, your body experiences oxidative stress, the same stuff involved in sun and age-related damage. Adding fat can also trigger inflammation, an immune response that can harm your cells. And these take a toll on the body, leading to higher rates of cardiovascular disease and type 2 diabetes.

For example, studies in 2003 and 2005 suggested that weight fluctuation can increase the likelihood of hyperinsulinemia - too much insulin in the blood - and eventually lead to metabolic syndrome, a collection of conditions that predispose you to cardiovascular disease. Other research has shown that weight cycling increases other cardiovascular risk factors, like unhealthy blood lipids and high blood pressure. That, along with the inflammation from weight gain, increases the development of plaques in the arteries and around the heart, which can lead to heart attacks.

Given all of this, instead of dieting, you might try losing weight by ramping up your exercise regimen. But that's another healthy behavior that can be overdone. Take running. Running's great; after all, adding as little as 75 minutes of running to your weekly routine can reduce your risk of mortality. But if you start trading those 5Ks for marathons, you may lose those health benefits.

Studies have found that more than four or five hours per week of vigorous exercise - the kind where your heart is pounding and you're drenched with sweat - carries the same mortality risk as no exercise at all. And some studies suggests it actually increases your change of dying. That's probably because extreme endurance athletes put a lot of stress on their hearts, which can make them undergo physical remodeling: A change in the structure of the heart muscles that makes heart conditions more likely. And it's not just excessive cardio that can be a problem; you can overdo strength training, too.

Enter "rhabdomyolysis," a condition where damaged muscles release protein into the bloodstream, ultimately causing damage to the kidneys. There are a couple ways to get it, including overexerting your muscles by lifting more than you should -

- more than you should, or doing hundreds of sit-ups, push-ups, or squats in a single session. And anywhere from 10-50% of rhabdomyolysis patients develop acute renal failure, which can be fatal. 

Of course, literally working your muscles to death is the extreme end of things. Dieting and exercise can be good for you if you ensure you're eating nutritiously, making lasting changes, and not pushing your boundaries too far. Things tend to go wrong when people assume that if it's something healthy, then more is even healthier. But good health just isn't that simple. And if you watch SciShow regularly, hopefully, you're starting to imagine the human body a bit more complexly.

[slide]

Stefan: At the end of the day, you still need all your vitamins and nutrients, and cutting our entire groups without replacing those micronutrients can be detrimental. So, go ahead and make enough food for everyone at the table this Thanksgiving, but you can always scale down from five courses to three. As long as all of your guests get the nutrients they need, they will have something to be thankful for.

And we, of course, are thankful for the SciShow patrons who support this channel on Patreon. If you want to become a SciShow patron and help us make more videos like this one, you can go to patreon.com/scishow. And if you want to help support this kind of science exploration for all the younger members at your table, you could also check out patreon.com/scishowkids. There, you can get coloring pages and all kinds of fun activities to keep your little ones entertained or just to enjoy together. And happy Thanksgiving from us here at SciShow.

[outro]