Will providing food in randomised controlled trials produce greater weight loss effects?
The Nutrition Society Paper of the Month for January is from British Journal of Nutrition and is entitled: ‘Impact of food supplementation on weight loss in randomised-controlled dietary intervention trials: a systematic review and meta-analysis’. Authors: Cinthya Wibisono1, Yasmine Probst, Elizabeth Neale and Linda Tapsell.
To test the effectiveness of dietary interventions, adherence to the test diet by participants is essential as a lack of adherence can compromise study outcomes. Providing participants with a food to support weight loss, referred to as a supplement, might appear counter-productive. Yet, providing food supplements has been proposed as a means of improving behaviour and adherence, to pave the way for achieving the desired outcomes. What is unclear, however, is why food supplementation is effective and how this works for achieving weight loss.
We reviewed randomised controlled trials which provided food supplements to one or more study arms, and pooled the findings from individual studies to explore the effect of food supplementation on weight loss. Through our review, we established that in trials where only the intervention arm was provided with a food supplement, significant weight loss was observed compared to trials in which all study arms were supplemented with a food. We found that the act of providing food in trials appeared to enhance adherence to dietary recommendations, confirming that food supplementation seemed to be an effective means of improving behaviours and adherence to study protocols. However, we also identified other influential factors. Weight loss appeared enhanced when the diets prescribed were reduced in energy value; if the energy value of the food provided was integrated into dietary recommendations, and when behavioural support was provided through specific dietary counselling. This suggests that food supplementation was not a stand-alone factor for improving adherence to dietary interventions, or for attaining superior weight loss effects.
In summary, while food supplementation may help to augment effects of a diet on weight loss by providing motivation for behaviour change leading to increased adherence to dietary interventions, other mediating factors should also be accounted for. Supplemented foods must be incorporated into reduced-energy diets, and participants need to receive encouragement to instigate and sustain behaviour change, provided through dietary counselling.
The full paper ‘Impact of food supplementation on weight loss in randomised-controlled dietary intervention trials: a systematic review and meta-analysis’ is freely available until the 20th February 2017.
Nutrition Society Paper of the Month
Each month a paper is selected by one of the Editors of the five Nutrition Society Publications (British Journal of Nutrition, Public Health Nutrition, Nutrition Research Reviews, Proceedings of the Nutrition Society and Journal of Nutritional Science).