Small change approach not more effective than monitoring alone in preventing weight gain

Reviewed by Emily Henderson, B.Sc.Mar 7 2022

Managing overweight and obesity is challenging, and a new randomized controlled trial found that, contrary to earlier evidence, making small changes to caloric intake and physical activity levels did not prevent long-term weight gain better than monitoring alone. The research is published in CMAJ (Canadian Medical Association Journal) https://www.cmaj.ca/lookup/doi/10.1503/cmaj.211041.

The trial involved 320 sedentary adults aged 25–70 years living with overweight or obesity (body mass index between 25 and 39.9 kg/m²). The mean age of participants was 52.6 years, and 77% were female. They were randomized to either monitoring alone or to a small change approach that involved reducing caloric intake by 100 kilocalories per day or increasing physical activity by 2000 steps a day throughout the 2-year study.

"We found that the small change approach was not more effective than monitoring alone in preventing weight gain at 2 or 3 years in adults with overweight or obesity," writes Dr. Robert Ross, lead author and professor of health kinesiology at Queen's University, Kingston, Ontario, with coauthors.

"We had reasoned that the prevention of weight gain by making small changes in dietary intake or physical activity behaviors would be sustainable long term and would have clinical relevance, as even modest weight gain (0.5–1.0 kg/yr) in adults with overweight and obesity is negatively associated with important health outcomes," the authors write. Although the small change approach led to reduced weight at 3, 6, 12 and 15 months, by 24 months the prevention of weight gain did not differ from that associated with monitoring alone. On average, prevention of weight gain was observed in both arms of the trial.

Researchers were surprised at the study results, which contrasted with those of a previous study that showed the small change approach prevented weight gain over 3 years in a large sample of young adults with overweight. However, in a sub-analysis, the authors observed that weight gain was prevented in adults with overweight, but not those with obesity.

More than 63% of Canadian adults currently live with overweight or obesity, which contributes to chronic health conditions.

"The management of adults with overweight and obesity remains a public health challenge," the authors conclude.

A commentary published in the same issue of CMAJ discusses the lack of evidence on physical activity and chronic disease prevention in people with disabilities and calls for more research.