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Comment by pizza234 | Hacker News Reader

At the very least, this article should be clarified (or maybe, the backing research is garbage, which is a possibility).

In the context of weight management, the concept of "weight loss" should never be considered. This is because two people with same weight may have wildly different body compositions; this also applied to the same people but in different conditions.

A person may have different body compositions, but same weight, in two different periods of their life, which can very well be before and after starting a physical activity regime.

Regardless, I'm extremely skeptical. When one has a sedentary lifestyle, and turns to consistent sport activity, it's very typical to quickly lose fat and gain muscles for some time, which is in conflict with the research.

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> Regardless, I'm extremely skeptical. When one has a sedentary lifestyle, and turns to consistent sport activity, it's very typical to quickly lose fat and gain muscles for some time, which is in conflict with the research.

I have two thoughts on this. The first one is, I see more than a few chubby-or-more professional baseball players. Second, I see a TON of professional football players, specifically lineman, lose a hundred plus pounds because they're no longer trying to stay above a weight to remain competitive. The last one I read about just changed his diet. Had no desire to lift a weight or run a sprint ever again.

I don't track why people think weight loss is mostly exercise, where it is in fact almost entirely diet. This topic really makes people mad, I've never understood why. If you want to lose weight you can do so, safely, without ever exercising.

> When one has a sedentary lifestyle, and turns to consistent sport activity, it's very typical to quickly lose fat and gain muscles for some time

I've lived this experience. Exercise without diet will make you gain weight because muscles grow, and they're heavy, so your fat percent changes. This doesn't mean less fat, just a change in the ratio of muscle against fat.

Stored fat is a vast energy reserve, and exercise alone will not deplete it. Even if your metabolism increases because of your added muscle, it will eventually reach a new equilibrium. Exercise burns energy at a much, much lower rate than food can add it.

> In the context of weight management, the concept of "weight loss" should never be considered. This is because two people with same weight may have wildly different body compositions; this also applied to the same people but in different conditions.

Weight loss should _never_ be considered? How does that follow? Lots of people definitely need to lose weight.

I took it to mean that the goal is a reduction in adiposity. For most cases, weight loss will mean that, but it is also possible to become sarcopenic or chronically dehydrated, be lighter, and be in worse health.

Most studies look at more than just weight, they minimally assess BMI and ideally estimate body fat percentage. Some go further, looking at relative risk of other endpoints such as heart attack, heart failure, stroke, diabetes, injury, hospitalization, death, etc.

Take a person that with X% body fat and Y% muscles.

They start going to the gym; after some time, they'll have (random numbers) (X-2)% body fat, and (Y+2)% muscles.

On a scale, their weight will be the same, but in reality, their body composition (and looks) will be considerably different.

This is a very important concept. Beside the obvious case where somebody just looks at the scale, and they don't realize their progress, body composition as opposed to weight is extremely important when doing diets, because an improper diet may lead to excessive muscle loss, which is accidentally perceived as a success (on the scale) rather than a failure (because the body composition hasn't changed as intended).

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