Many factors have a role in weight loss and changing body composition. The main ones are your diet and activity levels, though genetics plays a role, too. Genetics can often be considered an excuse for a person's lack of progress when it comes to weight loss, though things may not be quite so clear-cut.
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Looking at the Percentages
Your body contains many different genes that can all affect weight loss in some small way, but some people are more predisposed to gaining weight, or struggling with weight loss, than others. According to Dr. Howard Eisenson of the Duke Diet & Fitness Center, genetics may account for up to 50 percent to 70 percent of your weight variability, meaning those with poor genes may have a harder time losing weight.
Depending on genetics, certain people may respond differently to specific types of food. Dr. Brian Parks and Dr. Aldons J. Lusis of the University of California, Los Angeles, investigated the genetic response of mice when fed high-sugar, high-fat meals, similar to those you might find in a fast-food restaurant. Though the research was done on mice, not humans, the researchers noticed very different responses to the foods, which could indicate that some people crave fast food more than others or have a harder time avoiding high-sugar, high-fat foods.
Keeping It in the Family
Weight gain, or difficulty in losing weight, is sometimes attributed to having overweight or obese family members. While there may be some truth in this in terms of genetics, it's also true that you inherit bad habits, notes dietitian Juliette Kellow. If your parents or grandparents are overweight, it's more likely to be because of their lifestyle rather than any genetic condition. This is good news, however. While you too may have developed these bad habits over your developmental years, by breaking them you should be able to lose weight.
The Bottom Line
Though some severe genetic conditions, such as Prader-Willi syndrome, can cause traits that predispose obesity and weight gain, these are rare. It is far more likely that genetics influences your lifestyle and food choices, not your weight itself. While genes may mean you have a harder time controlling cravings, or feeling full, this doesn't mean weight loss is impossible -- you simply have to work harder to stay motivated, regulate your calorie intake and move more.