Don't let anyone tell you that so and so can eat tons of food and never gain weight because her metabolism is so wonderful. In the rare exception that she has an uncorrected hyperthyroidism, in which case she has many deadly and uncomfortable symtoms, she is only eating that much when you're looking or just saying it. Otherwise, she is eating less, exercising a lot, or just moving around for the normal purposes in life at a tenser and quicker pace than her heavier cohort who thinks she looks at pie and gains weight. Genetics, according to vast medical research, doesn't account for more than 10% of weight gain. It does account for a lot more than that in terms of where fat is deposited on the body or body type. Still, if your friend weighs 100 lbs., it is likely that she isn't eating more than most people in the course of a week than other people who sustain that weight. Same with 150lbs. or 200lbs..
Yes, there is much that a person can do to stimulate metabolism, such as eating protein, eating carbs, eating frequently and moving around at various paces often. That's environmental, not genetic. If you're heavy, try it. It's more about habits and eating a little too much too often than eating disorders , compulsive or emotional eating, and genetics for the average heavy person who gained 100 lbs. over 20 yrs.. You can do it without going on a strenuous and drastic Big Loser TV show. You don't need to spend money wildly. Just change little habits on a regular basis.