Vegan, paleo, keto, low-carb, low-fat, and the list of diets goes on. You most likely have had anecdotal experiences from friends swearing by a certain diet, but then another friend claiming the exact opposite. How is that possible?
Yes, all diets work. But no, not all diets work for you.
All diets work for at least a subset of people, but you may not be that subset
How a diet works for one but not for another is totally plausible. Genetics usually plays a role. Our genes affect our “sensitivity”, hence to the same stimuli you may not have the same response as someone else’s – as an example, cutting down on carbs may lead to robust result in one but negligible in another. This is the irony of why all diets work but not all diets work.
Fasting works because it is not a diet but a survival instinct
Fasting induces a beneficial response called “autophagy” in your body. Autophagy is like garbage disposal - it gets rid of the old and malfunctioned parts and recycles them into making new and robust components.
Yet autophagy is best thought of as a “survival mechanism” embedded inside your body. Fasting (without or reduced calories) pressures your body to make instant improvements in order to maximize its chance of survival. It is not a gentle dietary “nudge”; your body responds with full force as it is a survival instinct built in.
Fasting (and autophagy) works because after millions of years evolution still says so
The science behind autophagy is fascinating. But to highlight one aspect, autophagy is “universally conserved”, meaning it is a survival mechanism that has resided in you, me, mice and even yeast, despite how far we have diverged on the evolutionary paths. A feature that is “universally conserved” usually points to the fact it is hugely important to an organism and often plays a beneficial role to survival – hence it is “chosen to stay”.
Human clinical trial shows the same expected benefits
The ProLon diet, with proprietary formulations that mimic fasting, has been shown in a randomized clinical trial with the same benefits. The benefits on weight loss, improved blood pressure and cholesterol, and many more, are consistent and observed across genders and ethnicities (Caucasian, Black, Asian, Hispanic). What is more noteworthy is that even after trial participants returned to their normal diet after ProLon, without any dietary restrictions or changes, for at least 3 months such results were retained.
As of today we still do not fully know about all the science behind autophagy and fasting. But to take a bit of guess, how these results are long-lasting perhaps should not be surprising after all. For all we know, it triggers a “survival mechanism”, it is likely that the body would "choose" to induce beneficial changes that “matter”. Autophagy is also performed on cells across the body, not targeting a particular part, or a specific organ, or a one-off shed of body fat. Such thorough “overhaul” of the whole body likely has a role to play in producing lasting benefits.