I guess I would have to be considered a genetic outlier by most here. For all of my adult life, I followed a low fat, high carb diet: vegetables, fruits, pastas, breads (mostly breads without a lot of added oil), very few other added oils, very small amounts of lean white meats and fish, and even refined grains (bagels are a favorite) and some sugar (in processed foods like jams, cereals). I never dieted; I ate when and as much as I wanted. In the past 7 years, my fat intake has gone up some (nuts), sugars down, refined grains down (but more whole grains), and I went vegan. So pretty much being anti-LCHF, I'm like the devil to some here; and I guess you could say that I "doubled-down" on that with the vegan thing in the past 8 years.
Here's what is so weird. While there are posts here that people gained lots of weight on that diet, my BMI throughout my life has never been above 19, and now is around 18. When I went vegan, I dropped 15 pounds even though I didn't go vegan to lose weight (my guess is that was due to a reduction in calorie "density" of the food I am eating - whatever, it was unexpected). I'm sure that some here think that is too thin, but my doctor at the Mayo Clinic is very supportive. Blood sugar numbers have always been great. I'm not proselytizing about any of this, or bragging; neither of those is of any interest to me; we all are old enough to think and decide for ourselves. It's just crazy interesting to see how different people have such different outcomes with food.
You might think there's some other factor, like that I'm really active. I am in my first year of retirement and, yes, I'm very active right now, but there were many, previous work years when I didn't do much exercising at all. I have been a "binge exerciser" my whole life. So I don't think that's it; otherwise, my weight through life would not have been so constant (+/- 5 pounds, until the vegan drop).
I do have a poor sense of smell, which affects my sense of taste. Because of this or some other reason, I "eat to live" rather than "live to eat" (no love affair with food).
Clearly my body somehow is balancing my caloric intake with my caloric expenditure. So is it the genes? Maybe so and/or there are multiple pathways to healthy living. Just weird how the outcomes can be so different for people.