Study Finds Only Small Weight Loss Differences Between Brand Diet Plans

Bradley Johnston, PhD Scientist | Child Health Evaluative Sciences Hospital for Sick Children Research Institute Assistant Professor | Department of Clinical Epidemiology & Biostatistics  McMaster University Toronto, Ontario, Canada, M5G 0A4MedicalResearch.com Interview with:
Bradley Johnston, PhD
Scientist | Child Health Evaluative Sciences
Hospital for Sick Children Research Institute
Assistant Professor | Department of Clinical Epidemiology & Biostatistics
McMaster University Toronto, Ontario, Canada

Medical Research: What are the main findings of the study?
Dr. Johnston:

  • Our findings represent the first meta-analysis using advanced epidemiological methods to summarize popular branded diets for weight loss, trials having been investigated using randomized trial methodology.
  • Among the 48 original RCTs included in our NMA, low to moderate quality evidence showed that both low-carbohydrate and low-fat diets were associated with an approximate 8 kg weight loss at 6 months when compared to no diet. Approximately 1-2 kg of this effect was lost by 12-months.
  • Although statistical differences existed among several of the diet macronutrient classes, the differences were small and unlikely to be important to those seeking to lose weight.
  • Similarly, our results showed that although there are statistically significant differences between some of the brand named diets, these differences are small and not likely patient important.
  • In terms of potential effect modifiers, behavioural support was significant at 6-months (enhancing weight-loss by 3.23 kg) and exercise was significant at 12-months (enhancing weight loss by 2.13 kg)
  • Regarding our sensitivity analyses, Differences in weight loss were not clinically important based on risk of bias, missing data, baseline weight, gender, and those with and without specific health conditions
  • Overall, our findings suggest that patients may choose, among those associated with the largest weight loss, the diet that gives them the least challenges with adherence.

Medical Research: Were any of the findings unexpected?
Dr. Johnston:

  • Again, the weight loss differences between these diets were small with likely little importance to those seeking to lose weight, supporting the application of the named diet a patient is likely to best adhere to in order to lose weight.

Medical Research: What should clinicians and patients take away from your report?
Dr. Johnston:

  • As compared to no intervention, Low carbohydrate and low fat dietary programs are associated with the most weight loss over a 12-month time period.
  • Across interventions, Behavioral support (at 6 months) and exercise (at 12 months) enhanced weight loss.
  • The message here is that branded diets work for weight-loss, and that doing something that is self-enacted and structured to reduce weight (that is, diet and lifestyle modifications) is better than doing nothing.
  • Again, the weight loss differences between these diets were small with likely little importance to those seeking to lose weight, supporting the application of the named diet a patient is likely to best adhere to in order to lose weight.
  • Our results are specific to weight loss, not which diet is healthiest (e.g. reduction in cardiovascular risk factors)

Medical Research: What recommendations do you have for future research as a result of this study?

Dr. Johnston:

  • Given that differences between diets were of minimal patient importance, future trials should focus on preference-based randomization where patients are randomized to a dietary program of their choice (a dietary program they think they can best adhere to)
  • Although our study did not examine switching between diets, such a strategy may offer patients greater choices as they attempt to adhere to diet and lifestyle changes.
  • Further, and importantly, future studies should focus on longer-term follow-up, and interventions to improve adherence to dietary programs (such as text message reminders, micro-economic incentives)

Citation:

Johnston BC, Kanters S, Bandayrel K, et al. Comparison of Weight Loss Among Named Diet Programs in Overweight and Obese Adults: A Meta-analysis. JAMA. 2014;312(9):923-933. doi:10.1001/jama.2014.10397.