Why a low-calorie diet may not help everyone lose weight?

TORONTO: While eating a diet that's low in calories helps in shedding that extra kilos, it may not help individuals with difficult-to-treat obesity lose weight -- and keep it off, finds a study that emphasises the need for exercise among such people.

Understanding distinct obesity phenotypes is key to teasing out insights into individual variations in weight loss.

And for "diet-resistant" obesity -- patients in the bottom 20 per cent for rate of weight loss following a low-calorie diet -- exercise training should be prioritised, as it decreases fat mass and boosts skeletal muscle metabolism, according to the new research published in the journal eBioMedicine.

"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. And that's really going to help you lose weight," said Dr. Ruth McPherson, Professor at the University of Ottawa's Faculty of Medicine.

For the study, the research team mined clinical data from over 5,000 records. Ultimately, 228 files were reviewed and a subset of 20 women with obesity were identified to undergo a closely supervised exercise program made up of 18 progressive sessions using treadmills and weights done three times per week for six weeks.

Using bioinformatics and machine learning approaches to analyse skeletal muscle, the results indicate that exercise preferentially improves skeletal muscle metabolism and enhances weight loss capacity for individuals with obesity who are deemed diet resistant.

These are the type of patients with difficult-to-treat obesity who have often been accused of non-adherence when they have not lost weight with diet restriction.

The stakes are high: The number of people who are overweight or obese has grown to epidemic proportions globally and obesity is a risk factor in a slew of chronic diseases.

"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,a said Dr. Robert Dent, an endocrinologist at the varsity.

"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."

The study has the potential to help reshape the science of weight-loss programmes so they can be customised for individual patients.