November 7, 2014

Stephanie Ramage,ab Anna Farmer,abc Karena Apps Eccles,ab Linda McCargarab

aDepartment of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB T6G 2P5, Canada. bAlberta Institute for Human Nutrition, University of Alberta, Edmonton, AB T6G 2E1, Canada. cSchool of Public Health, University of Alberta, Edmonton, AB T6G 1C9, Canada.

It is well known that levels of overweight and obesity have increased significantly in Canada over the last 3 decades. While much research has been done on weight loss and weight maintenance, Canadians are still unsure of the best approach. In this review researchers examined all published studies that reported successful weight loss (defined as at least 5% body weight) and successful weight loss maintenance (defined as remaining at a body weight at least 5% below starting weight for 12 months) in adults (18-65 years old). A comprehensive screening of almost 3000 abstracts and a review of 260 full-text articles resulted in 34 key studies. Of those, 24 studies described both successful weight loss and maintenance and 10 studies examined just successful maintenance.

Weight Loss: Most of the studies with successful weight loss included a specific caloric intake level or calorie reduction (example: decrease intake by 300-500 kcal per day). Studies with a strong quality rating commonly recommended an intake of 1200-1500 kcal per day. Lower fat and higher fibre intakes were also common strategies used. There were 3 studies that examined different macronutrient ratios (example: high carbohydrate versus high protein). These studies were successful in creating weight loss but that was due to overall decreased calorie intake. No difference in weight loss was seen between different ratios of carbohydrate, protein, and fat. Most of the successful studies also included a physical activity prescription. In general, this was a weekly time goal with a suggested number of sessions per week (example: walking for 30 minutes per day, 5 times per week). Behaviour training was also common among successful studies including cognitive behaviour training or consultation with health professionals such as psychologists or registered dietitians. One specific technique commonly used was self-monitoring of food intake and/or physical activity in a journal.

Weight Maintenance: A variety of strategies were shown to successfully allow for long-term weight maintenance for a minimum of 12 months. However, all of these studies had a comprehensive initial weight loss phase where dietary intake, physical activity, and behaviour training were emphasized. This review confirmed the importance of calorie restriction as well as regular physical activity during the weight maintenance time period. Self-monitoring and cognitive strategies were also frequently reported among those studies successful in maintaining weight loss over time. This review did not observe different strategies for maintaining weight compared to those required for weight loss.

When Weight Loss or Maintenance was Not Successful Of those studies that were not successful in creating weight loss and/or maintenance, at least 1 out of these 3 strategies (food intake, physical activity, or behaviour change) was missing. More often, studies that were not successful had a “general” healthy eating focus instead of providing a specific calorie goal. Unsuccessful studies were also more likely to “encourage” rather than “require” increased physical activity or self-monitoring.

Conclusion: Overall, long-term vigilance in terms of dietary intake, physical activity and behaviour change continue to be of key importance for both weight loss and weight maintenance.

Reference: Applied Physiology, Nutrition, and Metabolism, Published on line Nov 4, 2013 doi:10.1139/apnm-2013-0026

If you intend citing any information in this article, please consult the original article and cite that source. This summary was written for the Canadian Society for Exercise Physiology and it has been reviewed by the CSEP Knowledge Transfer Committee.