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Comment by calvano915 | Hacker News Reader

Skepticism is important for any advice. MyPlate/USDA dietary guidelines are updated often, based on all the research and debunking that has happened before and since 1992. As I mentioned in another comment, it's a good place to start for most people. There is going to be some influences affecting their recommendations but most people can benefit from the overall approach.

A diet with high carbs should be mostly complex carbs. There is no minimum refined carb recommendation. The only recommendation is to limit added sugars to <10% of daily kcals. That recommendation may be reduced further in later revisions.

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I think we both agree that complex carbs are better than refined ones, and there are foods that are somewhat heavy in carbohydrates that are still good for you (kale, for instance).

I'm super skeptical that 45-65% of diet being carbohydrates is healthy though. Unlike proteins and fats carbohydrates don't have much nutritional value other than being useful for creating glucose. Since your body can synthesize glucose anyway, you don't really need that much. In terms of fiber, you can get that from vegetables. I don't necessarily think you have to cut out carbs completely and go on ketosis, but of all the major macronutrients carbs are the least useful, so it seems odd that they should be the vast majority of the diet, especially when we've known for at least a hundred years that carbohydrates are fattening. (I'm amused when people act like ketogenic diets are "new" -- historically high fat/low carb diets were common. And historically we didn't have an obesity problem.)

"the body can synthesize glucose" is a horribly misleading statement. The body can create glucose only by destroying protein and the amount it can create is limited by the buildup of toxic waste the process leaves behind. It's absolutely not the same thing as the body synthesizing vitamin A from carotene. You will be much better off eating carbohydrates, and 45% may be still too little.

I've read a book[1] -- by an actual doctor -- saying the exact opposite. If you think about it from an evolutionary standpoint, our ancestors would have had many times when food accessibility was scarce and they would have needed to maintain their strength through a long fast. An animal that burned muscle/protein over fat is an animal that wouldn't have survived long, that would be a terrible evolutionary disadvantage. The design of our body isn't stupid -- we store fat for a reason, so that we can burn it in times when food is scarce. Burning fat for energy is both normal and totally healthy.

From a personal standpoint, I barely eat any carbs and I've lost zero strength despite dropping 25 pounds. Apparently the diet that has made me thinner and increased my energy and mental clarity is the "dangerous" one, and the diet that has made everyone obese is "healthy" and "balanced".

[1] The Obesity Code by Dr. Jason Fung

Fats do not become glucose (with the exception of the glycerol from triglycerides...a minute amount of the total kcals from one trig) but they do become energy. The majority of energy is in fatty acids which have no pathway to glucose.

For example, it is believed that when we sleep our energy comes from fats. We are not doing anything exerting, so the process of (fat catabolism -> energy) >= energy needs. The brain needs glucose however, so it gets it from glycogen catabolism or protein catabolism (gluconeogenesis).

Edit: For some reason I cannot reply to the comment below. The recommendation is 45-65% based upon individual need. I've mentioned elsewhere in this thread that the brain can use ketone bodies.

I disagree that glucose = obesity as you seem to see it. Many, many things (nutrition, PA, stress, hormone issues, etc) are related to obesity.

A lot of what you emphasize is related to the lack of physical activity that the population no longer gets. If we truly want to solve obesity, it takes adjustments to diet and consistent purposeful physical activity. There's a lot that can be done with nutrition, but continuing our highly sedentary ways will always have consequences for health that nutrition alone will not completely solve.

Ketone bodies can be used by the brain. It prefers glucose, but you don't absolutely need it.

Lets say for a second you're right and you need glucose, though. 65% is a really high number, and we basically know exactly what it leads to (obesity).

Stop spreading misinformation. 65% is well within historical norms. People commonly ate that much or more, oils and meat used to be expensive.

I'm only giving advice that I've personally tried myself, and have seen it work. I actually have a coherent theory for why people get fat, you just have... anger

I think it's important to separate health and obesity when considering exercise. A large body of evidence shows us that exercise makes you healthy. A smaller body of evidence shows that exercise helps prevent obesity. But there is virtually no evidence that shows exercise has a large part to play in curing obesity.

I'm not comfortable with the word "designed." There is evolutionary adaptation, there is no design.

Would you have lost the same 25lbs. if you had just eaten less? In other words, does it really matter that you cut out carbs only? Are you chowing down on bacon and steaks?

A large percentage of our dietary need is strictly for energy (via glucose). Carbohydrates are most efficient over fats or protein to fulfill this need, among other needs like fiber intake. Complex ones work best, not only for sustained energy but other benefits as well.

Yes we have needs for micronutrients, which are acquired from all of the macros. If your diet is truly varied, balanced, and adequate (in all three macro categories) on a regular basis you will likely not be significantly deficient in micros.

Ok but, the only reason you would care about getting energy super efficiently/quickly is if you're an athlete. Also while glucose is certainly easier to burn, I've seen evidence that ketones are actually a better source of energy. Since we have an obesity epidemic, and the vast majority of (fat) people are on the diet you're proposing, I would suggest that energy efficiency is not exactly a high priority for most people. If we know that carbohydrates will cause weight gain (not just in humans, but in animals too -- there's a reason why they feed cattle grain and not grass), and we know that the biggest health problem we have right now is obesity, suggesting that people should eat a lot of carbohydrates seems like terrible advice.

And if you're going to suggest that the solution there is to decrease caloric intake, I also think that's bad advice. We know, from type 1 diabetes, that your body doesn't store fat if insulin isn't present. Certain foods have a much stronger insulin response than others, and not surprisingly carbohydrates have a much stronger insulin response than fats. IE, the notion that all calories are equal is not supportable by the scientific evidence. So if the culprit is insulin response, it would make much more sense to adjust what you eat and when you eat it, instead of measuring a number (calories) that isn't that useful anyway.

I disagree that the vast majority of people are following the dietary guidelines (they aren't just AMDRs) I base my assertions from. However, unless you/I present evidence for either case, it's a non-starter.

You're ignoring the complexities of insulin/components of a healthy diet/physical activity regarding carbohydrates. Technically, you could just eat only protein and survive. Doesn't mean this is the best advice and without many complications.

Of course carbs have higher insulin response as insulin regulates blood sugar uptake. Fats dont produce sugar, therefore insulin is unrelated. And many, many things cause weight gain, including fat intake for some.

Current guidelines allow for up to 35% of total kcals to be fats, with minimal/no risks. This encourages plenty of consumption of fats for energy. Perhaps if we continue our extremely sedentary ways then this will be raised higher in the future.

Obese people are obese because they eat--A LOT. I had a relative like that. The amount of food put away was epic.

I used to eat one (small) meal a day and I got fat. And then I switched my diet and I got not fat. I don't know why people make this stuff so personal, body chemistry is complicated and it's not that weird that certain foods are better than others.

Certain foods can be better than others, but the basic tenet "eat less than you need to power yourself" seems like it should be a consistent formula for anyone who adheres to the first law of thermodynamics.

I (and presumably many others) have used it with notable success, so when I see a data point that suggests it's not a valid approach, I immediately question the validity of that data point.

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