[thaumasiotes]

> weight loss is a poor metric for the healthiness of a diet

Most people are near-totally uninterested in their actuarial life expectancy. As a result, close to 100% of people on a diet are looking for weight loss.

Whether you should consider it a "health" objective is a more interesting question. From a Darwinian perspective, attracting a mate is much more important than whether you live to be 67 or 72.

[jjjensen90]

While you are right, it's not a choice between pure life extension on one side and pure weight loss for attractiveness... Because the "healthiness" of a diet, in my opinion, includes its sustainability (do you regain the weight immediately after stopping?), reliability (can you use the diet to reduce your weight in a controlled way?), compatibility with exercise (which can also work to make you more attractive and therefore more successful in the Darwinian sexual selection sense). Another reason that "scale weight" is a poor indicator of the healthiness of a diet is that depending on the diet you may be losing mass via fat loss, muscle loss, water loss, etc. What's more important is body fat percentage reduction if we are talking about both traditional Western attractiveness and (usually) physical health overall. There are diets and lifestyles that make you more attractive and also increase your life expectancy.

[deno]

Sustainability should be whether or not you are going around hungry. Because if not, then why would you ever stop the diet, or even worse go back to the old habits? Why would it be surprising that you would then gain your weight back?

And yeah muscle tissue is the important one. Any diet is sustainable until you burn through all your secondary reserves. How many buff vegetarians do you see? In my experience, you need to be a bona fide nutritional expert to maintain muscle mass on an exclusively plant-based diet.

[esailija]

Chronic reflux, constipation, nocturnal urination etc also make these diets unsustainable.

As buff vegan the proportion of buff vegans among vegans is probably the same as proportion of buff non-vegans among non-vegans. You have to be braindead not to be able to figure out what to eat as vegan to grow muscle, in the worst case I guess you can go to factory farmers who have mastered the art of growing muscle from plants..