Why Do Certain People Eat A Lot, But Never Gain Weight?

Dr. Ines Barroso, a researcher on genetics of obesity at the University of Cambridge, said there is little evidence to prove that certain people could consume more calories than others without exercising. However, Melanson said that there may be some physical differences that allow people to naturally consume the calories they ate without too much strict exercise. A large number of nervous system signals and hormones circulating in our blood tell us when we are hungry and when we are full. Melanson said this is called the appetite regulation system, and some people may have a more sensitive one.

An important hormone in this system is leptin. It can help us regulate our appetite for a long time, not the appetite for the next meal only. So people with a more sensitive system might eat at will at parties, and then feel not hungry for the next few days and eat little. “They can adjust their energy balance automatically because their appetite regulation system will say: ‘All right, we’ve eaten enough calories’,” Melanson said. 

Heredity could affect a person’s tendency to gain or lose weight. According to an article published in PLOS Genetics in 2019, researchers have identified more than 250 different DNA regions related to obesity. For this study, researchers compared healthy group of 1622 subjects with low BMI, severely obese group of 1985 subjects and control group of 10433 subjects with normal weight. They found that lean participants had fewer genes related to obesity. But Barroso, a co-author of the study, said that genes only cannot affect your weight. “We didn’t find certain gene that specifically prevents or induces obesity. It seems to be a continuum,” Barroso said, “There are also people who have genetic determinants of obesity, but they are just not obese.”

To sum up, the answer to this question is complicated: the tendency to gain or maintain weight is not destined, but it is not completely under our control. Melanson said that there is no genetic switch that allows some people to eat at will without gaining weight; and vice versa, gaining weight is not necessarily due to lack of self-control.

“All men are born different.”