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Are diet and activity key to managing weight and obesity?

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

In a study, recently published by the Canada Medical Association Journal, Robert Ross (Kinesiology and Health Studies) and team investigated whether making small changes to caloric intake and physical activity levels helps prevent long-term weight gain among adults with overweight or obesity.

The randomized, controlled trial involved 320 sedentary adults aged 25–70 years living with overweight or obesity (a body mass index between 25 and 39.9 kg/m2). The mean age of participants was 52.6 years, and 77 per cent were female. The researchers randomly divided participants into two groups: one simply monitored their weight by using a scale with no change to diet or exercise, while the other adapted a small change approach, which involved reducing caloric intake by 100 kilocalories per day or increasing physical activity by 2,000 steps a day throughout the two-year study.

Interestingly, the research team found that the small change approach was not more effective than the weight monitoring approach in preventing weight gain at two years into the study adults with overweight or obesity. Surprisingly, prevention of weight gain was observed in both arms of the trial.

“We thought that through these small changes to diet or exercise, participants would prevent weight gain and this would be sustainable in the long-term and be clinically relevant,” says Dr. Ross. “Although the small change approach led to reduced weight at three, six, 12 and 15 months, by 24 months the prevention of weight gain did not differ from that associated with monitoring alone. This was surprising as we hypothesized that the monitoring alone group would gain weight over the three years.”

The researchers were surprised by the results, which contrasted with those of a previous study that showed the small change approach to diet and exercise prevented weight gain over three years in a large sample of young adults with overweight. However, in a sub-analysis Dr. Ross and colleagues observed that weight gain was prevented in the adults with overweight, but not those with obesity.

As to why this happened, the authors speculate that people who enroll in a trial for weight management may already have some commitment to behavioral changes. Another possibility, they write, is that the effect of regular weight monitoring itself may have influenced the participants’ behaviour during the trial.

More than 63 per cent of Canadian adults currently are living with overweight or obesity, which contributes to chronic health conditions, including type 2 diabetes.

“We pursued this study because the prevalence of obesity is increasing worldwide, and without exception, no country on the planet has been able to demonstrate a decrease in obesity prevalence over the last four decades,” says Dr. Ross. “Because weight gain and obesity are such strong predictors of chronic disease, it is a public health problem.”

Dr. Ross believes we need to help people understand that preventing further weight gain has important health benefits as it is well established that weight gain is associated with an increase in health risk.

“The fact is weight loss is extraordinarily difficult to sustain for most adults,” he says. “So, while many Canadian adults have lost weight, unfortunately, that lost weight has been regained and very often to the point where they gain even more weight.”

Dr. Ross admits managing body weight and waist circumference in today’s hectic society is a challenge. That’s why small changes may be more palatable and sustainable for the broader population, rather than large changes, and that can go a long way in preventing weight gain in the first place.

Part of the challenge of achieving long-term weight loss is maintaining the significant behavioural changes required. Dr. Ross and his team plan to use the insights from this study to assess whether weight monitoring itself could be an effective means of preventing weight gain.

“Our behavioral colleagues think that there’s some great potential here, especially for adults with overweight. If we could prevent the transition from the overweight category to the obese category, that would be a real advance,” Dr. Ross says.

The study is now available on the Canadian Medical Association Journal website.