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Comment by strken | Hacker News Reader

I'm not sure that a reduction in body weight tells us all the relevant information. One of the possible downsides of fasting is loss of lean body mass, generally meaning muscle. This is a problem for older people in particular because it's harder to keep muscle as you age and because muscle protects from falls, frailty, etc.

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If a person is obese or morbidly obese, losing weight is the number one priority to increase overall health, lifespan, quality of life, etc etc.

Losing a bit of lean muscle mass along the way is not important compared to the huge health gains of losing the weight.

I agree that losing body fat is the number one priority, but I wish the research would focus on that rather than the number on the scale. Losing a bit of lean muscle mass along the way is important for its own sake, and also because it's a confounding variable for what I actually want to know, which is how much fat (not weight) a person lost.

Why does it matter?

When it comes to long term health outcomes, losing weight is the only thing that matters.

I don't think this is specific to fasting?

You need to be getting enough protein + strength training to maintain muscle in a caloric deficit

Weight loss is linked with some loss of lean body mass, regardless of the method used. Intermittent fasting has been shown to match any other calorie deficit in terms of lean body mass loss, rather than more as you're implying.

Regardless of how you lose weight the advice is and remains:

> Eat a minimum of 0.36 grams of protein per day, per pound of LEAN* body weight. Increasing to 0.5-0.7 grams of protein per day, per pound of LEAN* body weight for older adults or when undergoing weight loss.

*LEAN is a vital detail for overweight people, they commonly miscalculate protein requirements due to this. The easiest way for overweight people to determine their requirement, is just find an "ideal body weight calculator" online, enter height and gender, and then multiply THAT figure by 0.5-0.7.

For example a man who is 6' tall and 400 lbs should eat 62 grams of protein per day MINIMUM, but during weight loss 86-120 grams of protein per day. It is common, unfortunately, to read online people in this situation miscalculate this to 280(!) grams of protein per day which is incorrect and harms their weight-loss goals.

Do you have source for this? Because as you write I've always read to derive protein intake from the overall weight. That would indeed be a very important distance.

Yep, it is often repeated bad advice that was originally aimed at healthy weight adults and athletes and then misunderstood by people attempting to lose body fat. It is incorrectly repeated on hundreds of exercise sites and articles. Cite:

> Protein intake should range between 1.0-1.5 grams/kg of adjusted body weight. To calculate adjusted body weight, first calculate excess weight: Excess weight = current weight — ideal body weight (IBW). Adjusted body weight = IBW + 0.25 of excess body weight. This amount generally accounts for 20% to 30% of total caloric intake.

So a slightly more complex way of calculating roughly the same thing. I'd argue that for most people getting your ideal weight is a good enough approximation, and that using your overweight/obese body fat in your protein calculation is wrong by a lot no matter which calculation you use.

https://www.ajmc.com/view/chapter-2-clinical-nutrition-guide...

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