DNA vs. Diet: Healthy Weight Requires More Than Willpower

Looking for the root cause of your weight struggles? Sometimes it’s in your family tree.

When your diet doesn’t deliver the results you want, is it fair to blame your DNA? That depends. Your genes, your diet and your environment have a complex relationship, and all three influence how easily you gain and lose weight.

Furthermore, just as unique DNA combinations cause variations in hair color, height and other traits, they also ensure differences in the body’s ability to regulate weight. While for some people, genetic makeup contributes as little as 25 percent to their predisposition to being overweight, it accounts for up to 80 percent of the likelihood in others, according toHarvard Medical School.

That’s partly because of the number of genes that help determine weight, affecting characteristics including appetite, the body’s sense of fullness, metabolism, food cravings and the tendency to use food to cope with stress, the school says.

Insight into how those genes work together in individuals is increasing constantly, thanks to research nurtured by the Human Genome Project, which produced the first sequencing, or reading, of the human genetic code in the early 2000s.

“In terms of information, DNA is like printed text,” says David Adams, MD, Ph.D., a senior clinician with theNational Human Genome Research Institute. “Reading DNA through DNA sequencing has expanded access to the information in our genomes. The ongoing challenge going forward will be to expand understanding about what this information means for our health.”

Determining DNA’s Influence

Already, genetic research has enabled scientists to advance treatments for a variety of diseases — and to draw general conclusions about variations in genetic influence on people’s weight.

Genes probably play a major role in your difficulty maintaining an ideal weight if you have the following traits, Harvard Medical School reports:

• You’ve been overweight for much of your life.
• At least one parent is significantly overweight. If both parents have obesity, the chances that you will develop it are as high as 80 percent.
• You don’t lose weight even after increasing your physical activity and following a low-calorie diet for months.

If you have these traits, on the other hand, genetics are likely to play a smaller role:

• You are strongly influenced by the availability of food.
• You’re moderately overweight but can lose weight by exercising and following a reasonable diet.
• You regain lost weight during the holidays, after changing your eating or exercise habits, or when you’re stressed.

The study of how nutrition and genes work together enables much more individualized analysis, too. A team of researchers from the Broad Institute, Massachusetts General Hospital and Harvard Medical School have developed apolygenic score, or calculation of the cumulative effect of millions of genetic variants, that can quantify a person’s inherited risk of becoming overweight, the organizations say.

The researchers reported in a study that the 10 percent of adults with the highest scores weighed nearly 30 pounds more, on average, than the people with the lowest scores.

Customized Weight-Loss Treatments

“DNA is not destiny,” Kathiresan says. “We know that a healthy lifestyle can offset a genetic predisposition, although those with a high genetic risk likely have to work much harder to maintain a normal weight. Prevention strategies could be especially impactful early in life for these individuals.”

Adopting a healthy diet is one such strategy,says Lauren Poliakin, MD, a bariatric surgeon and weight loss physician at Adventist Health Simi Valley. “We have control over our diet and the types of foods that we’re eating, so as a first step, focus on developing a healthy eating plan that works for you,” she says. “Your meals and snacks should be low in simple carbohydrates and high in lean meats, fruits and vegetables.”

For people struggling to lose weight on their own, Adventist Health offers a variety of treatments, from bariatric surgery to nonsurgical options, which include weight-loss medications, dietary education, and access to exercise specialists and weekly support groups.

Reaching a healthy weight is only half of the goal of weight loss, Adventist Health experts say. Maintaining it typically requires long-term lifestyle changes, even when weight loss is achieved with prescription medications such as Ozempic and Mounjaro.

"These medications are designed to support your long-term health, similar to how blood pressure medications treat high blood pressure," explains Dr. Poliakin. "Weight loss medications are to be used an adjunct to diet, exercise, and lifestyle changes and are intended for chronic weight management. This means that some patients may use them long-term — just as they would with blood pressure treatments — to help maintain their progress. Continuing the medication helps reinforce the effort patients have put into their health, assisting them in keeping the weight off and experiencing lasting health benefits."

As with the predisposition to become overweight, the way people respond to weight-loss medication is also influenced by their DNA. Healthcare experts increasingly recommend tailoring treatment to patients’ unique traits.

“People who respond to one therapy may or may not respond to another,” saysLee Kaplan, MD, Ph.D., director of the Obesity, Metabolism and Nutrition Institute at Mass General and an associate professor of medicine at Harvard Medical School. “The strategy has to be to match the patient to the treatment that’s most effective and suited for them.”