Any newcomer to physical fitness or proper nutrition will, at some point, come across the notion of meal frequency — or, in layman’s terms, the number of meals eaten in a given 24-hour period. And while some popular sentiments preach the necessity of consuming five to six meals a day to “stoke the metabolic fire,” scientific evidence in general seems to say something very different. While more research is necessary to elucidate the effects of meal frequency on body composition, thermogenesis, fat metabolism, insulin responses, performance and other bodily functions, current data suggest that there is not enough support in favor of consuming more meals per day as an optimal form of eating.
A common argument in the school of thought supporting frequent meals throughout the day is the notion that it leads to increased caloric expenditure for processing the extra meals consumed. This calorie burn is said to be related to dietary induced thermogenesis, the body’s ability to produce heat from digesting food. Some proponents state that dietary induced thermogenesis increases significantly with more opportunities for the body to digest meals. A few studies have shown a positive correlation between meal frequency and thermogenesis, but many others have shown no such correlation between the two. In general, the body of evidence seems to demonstrate that partitioning nutrients over several meals does not necessarily lead to an increase in thermogenesis nor in metabolism.
This same line of thinking suggests frequent meals are more beneficial for appetite suppression and satiety. The logic behind this is that infrequent feeding leads to hypoglycemia, or low blood sugar, which physiologically encourages our bodies to crave simple sugars to replenish blood glucose levels. However, the data supporting this hypothesis are inconsistent and do not indicate any convincing correlations. Some studies have indeed shown that more meals throughout the day are helpful in reaching fullness and promoting hunger-related hormones, while others suggest the opposite. It seems that individual factors play a more significant role in daily nutrient partitioning.
Then, you might ask, what about insulin levels? Insulin is a hormone that is related to blood sugar levels; would huge spikes in insulin from infrequent meals not cause an increased storage of fat? Not quite. Several studies have supported the hypothesis that frequent meals aid in balancing blood glucose levels and insulin, but they have not shown that fat metabolism is greatly affected by a change in meal frequency. In layman’s terms, although insulin levels are regulated by increased meal frequency, insulin does not necessarily affect fat loss. Caloric intake seems to be much more important for fat metabolism and accumulation than is insulin.
So far we have only discussed the hormonal and chemical factors of the equation. Studying the relationship between meal frequency and body composition — specifically, its impact on fat-free mass, fat loss and body fat percentage changes — would shed more light on the issue. Fat loss and body fat percentage are common markers of body composition, but it is important to mention fat-free mass as well. Fat-free mass refers to muscle mass, skeletal mass and anything that is not fat in the body. Preserving fat-free mass, mainly muscle, is important for maintaining strength, performance, and metabolic function. Decreases in fat-free mass usually means that muscle is being broken down for fuel. Similarly, decreases in muscle mass can indicate that the body is undergoing too much stress from exercise or excessive caloric restriction.
A team of researchers recently conducted a meta-analysis of 15 studies on meal frequency. They carefully selected the 15 studies from a selection of 327 by using a rigorous list of criteria to ensure the studies chosen were relevant. Their meta-analysis accounted for fat-free mass, fat loss and body fat percentage. Their findings seemed to indicate that fat-free mass retention somewhat correlated with increased meals. However, after preliminary permutation tests were conducted on nine studies chosen from the original 15, the correlation was no longer significant. In addition, sensitivity analyses revealed that one study, when removed from the group, made the correlation between fat-free mass retention and meal frequency lose its significance. Fat loss seemed to have similar results. There was a general trend of increased meal frequency correlating with fat loss, but the significance of the correlation was based entirely on that same study. Once that study was removed from the analysis, the correlation was nullified. Permutation tests also showed that changes in body fat percentage did not have a significant correlation with meal frequency. Selective analysis also revealed that another study heavily influenced the correlation. Once that study was removed from the analysis, the correlation became insignificant.
Scientific research and inquiry is driven by skepticism, innovation and experimentation. The studies I have referenced for this article have all utilized their resources to attempt to answer compelling questions about meal frequency and related topics. The data mentioned here do not ultimately decide that a certain meal frequency is the healthiest and best way to consume food. Rather, it offers valuable information about what some of the general research has indicated thus far. It seems that there are not enough data to conclusively say that a given meal frequency is most optimal. To further answer that question, as many other scientific phenomena, more research should be conducted.
Let us not forget that research is also only so relevant. There are so many individual factors to consider with meal frequency that it would likely be more worthwhile for a given person to find the meal frequency that best fits his or her personal lifestyle and goals. I would also suggest that any person striving to improve his or her body composition should focus on their overall caloric and macronutrient (protein, carbohydrates and fat) intake, as well as eating micronutrient-dense and fibrous food sources.