Can’t lose weight by dieting alone? Researchers have bad news for you

For those who starve themselves to cut calories but still don’t see results — you’re not alone.

Researchers at the University of Ottawa have identified a separate group of obese people who are especially resistant to losing weight through dietary changes alone, according to a report published on Wednesday in The Lancet’s eBioMedicine journal.

The findings contradict a long-held belief that diet alone is enough to bring about significant weight loss, with exercise added as a supplemental treatment to help boost the benefits of healthy eating.

“If you look at a large group of people who are overweight and trying to lose weight, they don’t respond to exercise very much. But now we’ve found that people in this [diet-resistant] obesity phenotype really do,” said endocrinologist Dr. Robert Dent, who collaborated with Ottawa colleagues Drs. Mary-Ellen Harper, Chantal Pileggi and Ruth McPhereson on the study.

“What the findings are telling us is that when we see individuals with obesity who don’t respond to dietary restriction, they should be shunted over to physical activity,” Dent explained in a statement for the university’s newsroom.

Those considered to have “diet-resistant” obesity fall in the bottom 20% for the rate of weight loss while following a low-calorie diet. Those are the folks for whom exercise should be prioritized, the doctors argue.

Based on clinical records from more than 5,000 patients, 20 such women were asked to participate in a workout regimen designed to analyze changes in skeletal muscle metabolism — one critical indicator of health in metabolic patients.

Fat metabolism in the skeletal muscle is regulated by the mitochondria, and those with “diet-resistant” obesity show lower mitochondrial activity in their bones than those with “diet-sensitive” obesity, according to the researchers.

Participants were put through a total of 18 workout sessions, three times a week for six weeks, involving treadmills and weightlifting.

For the group already at a mitochondrial disadvantage, exercise was shown to boost activity in the skeletal muscle, while those with comparably higher mitochondrial activity at the start of the experiment saw no added benefits in that regard.

For decades, “diet-resistant” patients have been accused of failing to adhere to a low-calorie meal plan, based on a lack of pounds shed. Now, researchers hope their new approach will lead to more tailored care.

“It’s exciting and important work. These findings have clinical implications and reveal molecular mechanisms that will drive research for many years to come,” said Harper, whose team hopes to soon relaunch their study with an even larger cohort.

Obesity has been called an epidemic here in the US, where more than a third of adults (41.9%) age 20 and older weigh too much, according to Centers for Disease Control statistics. Add overweight adults who fall just short of clinical obesity and the percentage rises to a staggering three-quarters (73.6%).

The consequences of carrying too much weight are high — with an increased risk for developing deadly and debilitating diseases across the board, including diabetes, heart disease, musculoskeletal disorders and several types of cancer. The condition is also known to weaken the immune system, which makes overweight people more susceptible to illnesses, such as COVID-19.

“For those individuals who have obesity and who’ve had enormous difficulty losing weight, the message for them is: You are in a group of individuals for whom exercise is particularly important,” McPhereson added. “And that’s really going to help you lose weight.”