Bariatric surgery is recommended by the National Institutes of Health for people with a BMI above 40. These types of procedures can include a laproscopic band that limits the amount of food that can enter the stomach or a removal of a portion of the stomach (bypass).
In both cases the surgery will be effective for dramatic weight loss, recovering from diabetes and other related cardiovascular disease risks.
This doesn’t have anything to do with special diets or food choices, it’s just a matter of eating less total food.
If there was some other answer for weight loss beyond calories in vs out, then bariatric surgery couldn’t possibly work.
The next time you hear someone say that weight loss is any more than calories you can be sure that they don’t know what they’re talking about.