Nutrition

January 25, 2015

Are Frequent Meals Beneficial for Body Composition

Conventional wisdom states that eating small, frequent meals helps to optimize weight loss. In theory, eating frequently enhances a phenomenon called the thermic effect of food (TEF), which results in more energy expended after consumption of the meal. What’s more, some postulate that multiple meals spaced throughout the day prevents the body from going into “starvation mode,’ thereby keeping metabolism perpetually elevated.

There also is speculation that frequent feedings are beneficial for anabolism. This is based on the premise of a limit to how much protein can be used to maximize protein synthesis. It therefore follows that large boluses of protein result in extensive oxidation of amino acids, preventing their use in tissue building purposes.

Despite a seemingly logical rationale, the efficacy of consuming frequent meals to optimize body composition has not been well established in long-term studies. In an attempt to gain clarity on the topic, my lab recently carried out a meta-analysis where we pooled the data from all meal frequency studies. The analysis was a collaboration with my colleagues and frequent partners-in-science, James Krieger and Alan Aragon. Here’s the scoop…

What We Did
A thorough search of all English language journals was conducted for studies with the following inclusion criteria:
1. Randomized controlled trial
2. Compared unequal feeding frequencies of less than or equal to 3 meals a day with greater than 3 meals a day
3. Had a study duration of at least 2 weeks
4. Reported a pre- and post-intervention measure of body composition (body mass, body fat, lean mass)
5. Was carried out in human participants >18 years of age

A total of 15 studies were identified that met the criteria outlined and provided adequate data for analysis – several of these studies went back as far as the early 1960’s! The studies were individually coded and a randomly selected number of them were subsequently recoded to ensure accuracy. The coded studies were then pooled and statistically analyzed to determine what, if any, body composition differences existed between feeding frequencies.

What We Found
There was no effect of the number of daily meals on body mass (i.e. weight). Alternatively, initial analysis did show a positive association between feeding frequency and reductions in fat mass. Here’s the kicker: a sensitivity analysis showed that a single 2-week study by Iwao et al. highly affected results – when this study was removed from analysis, the effect of meal frequency was no longer significant. Similarly, body fat percent was initially shown to correlate with greater decreases in body fat percentage, but the results were highly affected by a single study by Arciero et al. whose removal rendered the results insignificant. There was a trend for greater increases in fat free mass with higher meal frequencies, but again the results were primarly attributed to the Iwao et al. study.

Commentary

The results of our analysis do not support a tangible benefit to eating small frequent meals on body composition as long as daily caloric intake and macronutrient content is similar. The theory that a greater feeding frequency increases post-prandial thermogenesis is fundamentally flawed. As shown in the accompanying table, a typical meal results in a TEF of approximately 10%. Since the TEF is dependent on the number of calories consumed in the meal, the net thermic effect is the same for 3 versus 6 meals on a calorie-equated basis. There also is no evidence that the body goes into “starvation mode” when you go without food for more than a few hours as commonly claimed in fitness circles. I covered the research on this in a recent T-Nation article.

The studies in question lasted varying amounts of time and many used recall food diaries to assess caloric intake, which have been shown to lack accuracy in reporting. However, several studies were carried out in metabolic wards where every morsel of food and every step of activity was carefully monitored – these studies showed no benefit to higher meal frequencies, providing further confidence in the validity of our findings.

A primary limitation of the analysis was that all studies to date were carried out in sedentary individuals. Thus, results cannot necessarily be generalized to those involved in regular exercise, particularly resistance training. There is compelling evidence that the muscles are sensitized to protein intake for at least 24 hours after a lifting session, suggesting a potential benefit to frequent feedings with protein rich foods in the post-exercise period. Whether this translates into greater long-term muscle growth remains to be determined.

It also isn’t clear if our findings are applicable to diets that include higher daily protein intakes. All of the studies analyzed used low to moderate protein doses, with the exception of the study by Arciero et al. Interestingly, this study did show significant improvements in body composition when an energy-equated high-protein diet (approximately 34% of total calories) was consumed in 6 versus 3 daily meals.

Take Home Points
The number of daily meals consumed does not appear to have much if any impact on changes in body fat, at least across a wide spectrum of feeding frequencies. Thus, the decision on how many meals to eat from this standpoint should come down to personal preference: if you find a benefit to having the structure of multiple meals throughout the day, then go for it; on the other hand, if you prefer to eat less frequently, that’s fine as well. The most important factor in this regard is achieving a negative energy balance, as well as ensuring that adequate dietary protein is consumed.

Although our analysis did not show differences between meal frequencies with respect to lean body mass changes, there is a logical basis for a hypertrophic benefit to consuming several protein-rich meals in those involved in regular resistance exercise. The anabolic effects of a meal last a maximum of 6 hours or so. Thus, consumption of at least 3 meals spaced out every 5 to 6 hours would seem to be optimal for keeping protein synthesis continually elevated and thus maximizing muscle protein accretion. This hypothesis needs further investigation in a controlled long-term study.