Have you ever felt like trying to lose extra pounds or keep them off is just more difficult for you than for other people? Recent research suggests you might not be imagining this. For some people, thanks to a combination of genetics and physiological differences, it really is easier to put on weight and harder to take it off.
Most of these people are women, who have a different genetic blueprint than men. Up until maybe 100 years ago, it was favorable for women to have extra fat stores and efficient metabolisms. This helped to ensure women's survival during times of famine and illness, and women's ability to nourish babies while pregnant and breastfeeding.
"We know for sure it's both genetic and environmental why some people are overweight and obese," says June Stevens, a distinguished professor at the University of North Carolina at Chapel Hill.
The genetic differences that determine a person's tendency to gain weight are less noticeable in environments where exercise is a part of everyday life and where there is NOT an abundance of great-tasting, affordable food. Most Americans, of course, live in the opposite situation. Stevens describes it as an "obesogenic" environment: a set of circumstances that encourages people to eat and drink more calories than they expend, and thus become obese.
Here are some of the possible reasons why the weight loss odds could be stacked against you, making it feel like you just can't lose weight:
You have a low resting metabolic rate, and high metabolic efficiency.
If you have a lower resting metabolic rate, your body spends fewer calories maintaining your body at rest than someone your size with a higher rate. And, if your body is metabolically efficient, it burns fewer calories while in motion.
Differences in resting metabolic rates and metabolic efficiency may explain up to about 22 pounds of weight gain, says Victoria Catenacci, MD, a researcher with the University of Colorado at Denver. This could help explain differences in normal weight vs. overweight, but many researchers believe that higher levels of excess weight (clinical obesity) are probably a result of excessive food intake and/or low physical activity.
2. You are female.
There are a number of reasons why men have the weight loss edge over women.
First of all, men have more muscle mass, compared to women, and women have a higher percentage of body fat than men. Muscle tissue burns more calories at rest than fat tissue. So it's no surprise that men's resting metabolic rate tends to be significantly higher than women's.
Also, women often deposit extra body weight in the hips, legs, and buttocks, while men tend to store extra weight in the midsection, says Robin Duncan, PhD, a postdoctoral fellow at University of California Berkeley's Department of Nutrition Science and Toxicology. Extra fat around the gut is more actively recruited during times of energy need and thus may be easier to lose than fat on the legs and hips, explains Duncan.
Further, because men tend to be larger than women, they tend to burn more calories doing the same exercise as women.
"If they both run at the same pace for one hour, the woman will burn 500 calories, for example, while the man will burn closer to 700 calories," says Catenacci.
As if this weren't unfair enough, men also seem to be better at suppressing hunger when presented with food, according to findings of a recent study.
After 23 healthy, non-obese people fasted for 17 hours, researchers used cognitive inhibition techniques to try to suppress thoughts of hunger. They found that the technique significantly lowered the desire for food only in men. Subsequent brain scans of the men showed a decrease in activation in brain regions that are known to play a role in processing our awareness of the drive to eat.
You experience hunger, satisfaction, and stress differently than others.
Stevens believes that differences in how people experience hunger and cope with stress are important in determining who becomes overweight and who doesn't.
"Individual genetic differences in the numerous hormones and peptides made by the gut, brain, and fat cells (that regulate appetite, hunger, and satiety) may play a big role in predisposition to obesity and difficulty losing weight,” says Catenacci.
Researchers are only beginning to understand what might be at play here, and how it affects what and how much a person eats.
4. You don't like to exercise (it could be in your genes).
According to Daniel Pomp, PhD, from the University of North Carolina at Chapel Hill, animal research suggests that 25%-50% of an individual's propensity for voluntary exercise is under genetic control.
Pomp studies mice that genetically prefer to exercise because they were bred for high levels of wheel running. Expect more research in the next few years on "exercise genes" and how they might also be at play in humans.
Your mother ate a high-fat diet while pregnant.
There is some preliminary research in primates that suggests eating a healthy, moderate-fat diet is important for the future weight and health status of the developing fetus, regardless of whether the pregnant mother was obese or lean.
6. What you ate as a toddler could be affecting how easily you gain weight as an adult.
Research from Raylene Reimer, PhD, RD, a researcher from the University of Calgary, has indicated that the food we eat affects how active certain genes are in our body. "In particular, we believe that our diet has a direct influence on the genes that control how our bodies store and use nutrients," explains Reimer.
In Reimer's research with rats, a group that ate a high-protein diet when young packed on much more weight and body fat as adults compared to another group of rats raised on a high-fiber diet.