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Comment by xboxnolifes | Hacker News Reader

> The general advice, even from my primary care physician, has been that anything less than 1200kcal/day is dangerous and is crash dieting.

Wouldn't this advise need to keep in mind absolute height? BMI tracks the ratio between the height and weight, but it does nothing to tell the difference between a short thin person and a taller heavier (but same BMI) person. The latter which would need more calories than the former. I know people who eat ~400 kcal less than me per day, because they are shorter and similarly thinner. Following that why wouldn't their crash diet threshold be sufficiently lower?

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My understanding is that 1200 kcal is independent of height or weight. I was told that the rough calculation was based on the lower estimate of basal metabolic rate and then subtracting a couple hundred kcal.

We both come from a South Asian background and discussed how the number would change for a home cooked vegetarian diet which is more nutrient dense but low in protein, and I was told that would lower it below 1200, but he didn't feel comfortable recommending that diet unsupervised. He emphasized that I should decrease calories by removing carbs, then fats, then proteins. And that I should prioritize eating proteins above fats and carbs, especially if I planned on increasing the amount of exercise I did.

I asked him if the 1200kcal was net or gross. For example if I did 2 hours of moderate exercise, should I eat back 400kcal+ to maintain a net 1200kcal. He didn't have an answer for me, other than saying, if I start to feel weak or lightheaded I should immediately stop exercising. I don't have pre-existing conditions related to blood glucose, but I imagine that would would change many of these guidelines. I was told to stay mindful of hydration.

The stories I hear of fasted work outs is the reason I asked him about low calorie diets. My non professional intuition makes me believe that even intense cardio should be okay, but moderate or heavy resistance training should be avoided on a low calorie diet.

Your understanding is incorrect, and not based on any actual science. Energy needs are highly correlated with body size (and other factors like activity level and genetics).

There is no reason to avoid resistance training.

The few times I have tried to do intensive resistance training, above 60% of my PR, I have started feeling weak after the second or third day. I don't use caffeine for pre-workout. This might not be common, but I personally experienced a significant increase in exercise induced syncope and near-syncope when fasted.

I also imagined that muscle recovery would be less efficient or take longer from a fasted state. I have hit rowing/ERG goals and made time improvements so I feel comfortable saying that fasting doesn't hinder my cardio.

I understand that energy goals are correlated with body size, we were discussing a general minimum kcal threshold for unsupervised dieting. I am unsure why you feel estimated BMR/RMR - 200 kcal is unscientific. I was told that without supervision, it would be hard to ensure proper nutrition on a very low calorie diet. Additionally, he expected that some people would fall into a binge-restrict cycle because they can't sustain their usual energy level.

I was additionally curious because there have been days I forget to eat, and thinking back I realized my total calories for those 24 hours totaled less than 600 kcal.

Basal or resting metabolic rate varies tremendously between individuals, primarily based on body size. There is no scientific support for your claim of "1200 kcal is independent of height or weight".

Fortunately it's fairly cheap and easy for people in developed countries to obtain an RMR test. This can then be used as a personal baseline to calibrate diet plans.

https://www.bodyspec.com/what-is-rmr

The argument I've heard is that the other nutriments needs (vitamins, minerals, etc) don't scale as much with height. So even a very short person would have a vitamins/mineral deficit on less than 1200KCal per day.

How true is it? I don't know. But even then I don't see why they couldn't take multivitamins.

Many American diets are calorie/energy rich and nutrient poor. If you're eating 400 calories of healthy food you're probably getting several times the vitamins and minerals of the average American eating 2500 of fried, sugary food.

It's probably a mistake to connect the two.

Beef is very nutrient rich.

Yes, we Americans overeat beef / Hamburgers, but I don't think anyone eating burgers is at huge risk of malnutrition... as much as a risk of heart problems, diabetes, cholesterol, etc. etc.

It turns out that a standard burger with beef, ketchup, lettuce, onion, and bread covers most of your macro, and even micro-nutrients. It also is way overboard on salt and fats, but... that's not the particular problem here.

One of the bigger problems vegetarians have is finding a proper replacement of meat and all of the easy nutrients meat contains. All amino acids, various vitamins, iron, etc. etc. There's a fair amount of nutrients here.

And even the worst McDonalds burger contains a variety of lettuce / onions / ketchup that covers few nutrients that beef is missing (ex: Ketchup has Vitamin A, Potatoes / Fries has Vitamin C).

>And even the worst McDonalds burger contains a variety of lettuce / onions / ketchup that covers few nutrients that beef is missing (ex: Ketchup has Vitamin A, Potatoes / Fries has Vitamin C).

The amount of lettuce, tomatoes and onions is so minimal I doubt it contributes to your vitamin intake in any useful manner. If you eat a salad you get 50x that amount of those vitamins.

"Yes, we Americans overeat beef / Hamburgers, but I don't think anyone eating burgers is at huge risk of malnutrition... as much as a risk of heart problems, diabetes, cholesterol, etc. etc."

Pretty strongly disagree here. US Beef consumption is about the same as in early 1900's, which was a time where personal health in several metrics was far better. (Weight being the obvious one)

Always very skeptical when people talk about cholesterol, it's a really nuanced topic, but the average person seems to be stuck in the 1970's with "cholesterol bad". Thinking high ldl is always bad is only slightly better.

It can be frustrating how studies always lump in processed meat with unprocessed meat. Unprocessed meat is nearly google-proof, since every media outlet is busy broadcasting the evils of "red and processed meat" like they're inseparable. Seems like the cholesterol argument regarding meat itself is basically the main one left.

Yes, beef is an excellent nutrient, but my point is that the majority of calories in a typical burger meal do not come from sources like beef. A Big Mac meal only has 180 calories from beef, and 1320 calories total. The vast majority of calories in the american diet are sugars and oils.

If you eat only the beef and veggies from a Big Mac three times a day you'll get plenty of vitamins and minerals with minimal calories (~650 calories)

If you eat the three entire Big Mac meals you won't get any more essential nutrients to speak of and you'll consume far too many calories (3960 calories)

The average american has junk to cut from their diets with no nutritional loss whatsoever. Typically fried and sugary foods.

You can supplement all your micronutrients with barely any impact on calories consumed, so this is going to depend specifically on what you’re eating/supplementing.

It is possible to have an adequate intake of proteins and of most vitamins and minerals with only about 600 to 800 kcal.

Practically pure proteins can be provided by turkey breast or chicken breast, adding e.g. around 300 kcal for an adequate daily protein intake, and the rest of the food can be composed of non-starchy non-sweet non-oily vegetables, which provide only about 20 to 50 kcal per 100 grams. One could eat more than 1 kg of various such vegetables without exceeding 800 kcal.

There remain a few things that would have to be taken from supplements, e.g. omega-3 fatty acids, vitamin B12, vitamin D3 and vitamin E (which is abundant only in high-caloric food, like olive oil or almonds). The simplest is just to take one pill per day of those offered by various vendors, which include all the essential vitamins and minerals, to be sure that none of them is insufficient.

A little vegetable oil would be needed for linoleic acid.

Yes, it's surely intended in the same spirit/based on the same averaging as the 2M/2M5 (fe-/male) cal RDA.

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