Its not about eating healthy food, obesity is about the over consumption of food. You can maintain a healthy weight eating hamburgers and fries every day. The problem is portion size.
- food quantity
- genetics
- physical activity or lack thereof
- food quality and make-up (plant / animal for instance)
- and an addictive element thrown in for some individuals
- microbiome activities
- epigenetics
- what you eat at a young age
If you listen to people who have had success with low-carb and/or keto diets, their comments almost always discuss how the way they feel about food changed. They weren't hungry and they felt more energetic. Just about 0 of them mention spending time tracking calories consumed or measuring calories expended.
On mouse models, these high fat high protein diets have improved brain functionality. http://www.cell.com/cell-metabolism/fulltext/S1550-4131(17)3...
Biggest issue effecting health is obesity which puts strains on your internal organs.