It’s commonly believed that consuming small, frequent meals optimizes fat loss. According to theory, go without eating for more than a few hours and your body shifts into “starvation mode.” Part of the starvation response is to slow down metabolism in an effort to conserve energy. Pretty hard to get lean when your metabolic rate isn’t cooperating. Conceivably, providing your body with a constant stream of nutrients prevents the starvation response by “stoking the metabolic furnace,” thereby enhancing the ability to burn stubborn body fat.
Or so the theory goes…
The Research
Despite a seemingly logical basis, however, the evidence generally doesn’t support metabolic benefits of increased meal frequency. A study in dogs did show that consuming four small meals doubled the thermogenic response compared to eating an energy-equated amount of food as a large single meal.9 A follow-up study by the same group of researchers found similarly beneficial thermogenic effects in humans from a greater feeding frequency.10 On the other hand, a number of other tightly controlled human and animal trials have failed to show increases in metabolism as a result of spreading nutrient intake over multiple meals.5,7,13,18,19
While acute studies on metabolism provide interesting mechanistic insight into the body’s immediate response to different feeding frequencies, the only thing that really counts is whether a strategy of eating more frequently enhances fat loss. And the only way to determine actual fat loss is through randomized controlled trials (RCTs) that study this outcome directly.
My lab carried out a meta-analysis to gain greater clarity on the topic. We searched back to the early 1960s to find any and all RCTs that compared feeding frequencies of less than or equal to three meals a day with greater than three meals a day. Studies had to last a minimum of two weeks, involve healthy adult men and/or women, and equate the number of calories consumed between conditions. A total of 15 studies were determined to meet inclusion criteria. The results of these studies were then pooled for analysis to determine what, if any, effects on body composition can be attributed to how often you eat.
The results?
Feeding frequency had no effect on overall bodyweight. This seems in line with the findings of the acute studies mentioned earlier. Interestingly, however, our initial analysis did reveal a positive correlation between fat loss and the number of daily meals consumed. Here’s the rub: A sensitivity analysis found that these results were almost exclusively attributed to a single study6— the effects all but disappeared when this study was selectively removed from analysis. A positive association also was initially found between meal frequency and reductions in body fat percentage, but again these results were unduly biased by one study1 whose deletion rendered the results inconsequential.
Fat-loss Findings
So what can we glean from our research? Contrary to popular belief, it doesn’t appear that eating small, frequent meals provides any meaningful benefits to fat loss. This was particularly apparent from the metabolic ward trials included in our analysis. As opposed to “free living” studies that allow subjects to self-report dietary habits (and thus have been shown to be quite unreliable), research carried out in a metabolic ward meticulously controls these variables; every morsel of food and every step of activity is carefully monitored by the investigators. Without exception, these studies showed no benefit to fat loss from higher meal frequencies.
Now a caveat to our meta-analysis is that we only included studies that matched caloric intake between feeding frequencies. This was necessary to rule out the potential for confounding from unequal energy consumption. However, some claim that the true benefit of an increased meal frequency is a better control over hunger, conceivably by regulating blood sugar and hormonal levels. If true, this in itself would promote a beneficial effect on fat loss given that weight management is basically a function of energy balance: take in more calories than you expend and you’ll gain weight; create a caloric deficit and you’ll lose weight.4 Thing is, research is conflicting on the topic. Although some studies have found that spacing out meals over the course of a day reduces hunger,14-17 others show no differences in satiety regardless of feeding frequency.3,12 Several studies have even found greater feelings of fullness from consuming three as opposed to six daily meals.11,13 Considering the body of literature as a whole, evidence remains weak that eating frequent meals helps to control hunger; any beneficial effects are likely specific to the individual.
Personal Preference
The take-home message here is that eating small, frequent meals appears to have little if any effect on reducing body fat. From this standpoint, meal frequency should therefore come down to personal preference: choose whatever frequency fits your lifestyle. Focus on what’s important to achieving fat loss: creating a negative energy balance and consuming adequate dietary protein.
Aside from fat loss, there is a compelling reason why feeding frequency may have important implications on body composition. Namely, the anabolic effects of a meal have been estimated to last approximately five to six hours based on the rate of postprandial amino acid metabolism.8 Given that you’ll generally spend at least 16 hours of the day awake, you thus need at least three protein feedings to maximize anabolism. Indeed, recent research indicates that spreading protein intake out over four daily servings increases muscle protein synthesis to a greater extent than consuming the same amount of protein in two larger servings.2 So eating a minimum of three daily meals spaced out no more than every five to six hours is a prudent strategy to promote lean muscle.
References:
1. Arciero, PJ, Ormsbee, MJ, Gentile, CL, Nindl, BC, Brestoff, JR, and Ruby, M. Increased protein intake and meal frequency reduces abdominal fat during energy balance and energy deficit. Obesity (Silver Spring) 21: 1357-1366, 2013.
2. Areta, JL, Burke, LM, Ross, ML, Camera, DM, West, DW, Broad, EM, Jeacocke, NA, Moore, DR, Stellingwerff, T, Phillips, SM, Hawley, JA, and Coffey, VG. Timing and distribution of protein ingestion during prolonged recovery from resistance exercise alters myofibrillar protein synthesis. J. Physiol. 591: 2319-2331, 2013.
3. Cameron, JD, Cyr, MJ, and Doucet, E. Increased meal frequency does not promote greater weight loss in subjects who were prescribed an 8-week equi-energetic energy-restricted diet. Br. J. Nutr. 103: 1098-1101, 2010.
4. Hall, KD, Heymsfield, SB, Kemnitz, JW, Klein, S, Schoeller, DA, and Speakman, JR. Energy balance and its components: implications for body weight regulation. Am. J. Clin. Nutr. 95: 989-994, 2012.
5. Hill, JO, Anderson, JC, Lin, D, and Yakubu, F. Effects of meal frequency on energy utilization in rats. Am. J. Physiol. 255: R616-21, 1988.
6. Iwao, S, Mori, K, and Sato, Y. Effects of meal frequency on body composition during weight control in boxers. Scand. J. Med. Sci. Sports 6: 265-272, 1996.
7. Kinabo, JL, and Durnin, JV. Effect of meal frequency on the thermic effect of food in women. Eur. J. Clin. Nutr. 44: 389-395, 1990.
8. Layman, DK. Protein quantity and quality at levels above the RDA improves adult weight loss. J. Am. Coll. Nutr. 23: 631S-636S, 2004.
9. LeBlanc, J, and Diamond, P. Effect of meal size and frequency on postprandial thermogenesis in dogs. Am. J. Physiol. 250: E144-7, 1986.
10. LeBlanc, J, Mercier, I, and Nadeau, A. Components of postprandial thermogenesis in relation to meal frequency in humans. Can. J. Physiol. Pharmacol. 71: 879-883, 1993.
11. Leidy, HJ, Armstrong, CL, Tang, M, Mattes, RD, and Campbell, WW. The influence of higher protein intake and greater eating frequency on appetite control in overweight and obese men. Obesity (Silver Spring) 18: 1725-1732, 2010.
12. Leidy, HJ, Tang, M, Armstrong, CL, Martin, CB, and Campbell, WW. The effects of consuming frequent, higher protein meals on appetite and satiety during weight loss in overweight/obese men. Obesity (Silver Spring) 19: 818-824, 2011.
13. Ohkawara, K, Cornier, MA, Kohrt, WM, and Melanson, EL. Effects of increased meal frequency on fat oxidation and perceived hunger. Obesity (Silver Spring) 21: 336-343, 2013.
14. Smeets, AJ, and Westerterp-Plantenga, MS. Acute effects on metabolism and appetite profile of one meal difference in the lower range of meal frequency. Br. J. Nutr. 99: 1316-1321, 2008.
15. Speechly, DP, and Buffenstein, R. Greater appetite control associated with an increased frequency of eating in lean males. Appetite 33: 285-297, 1999.
16. Speechly, DP, Rogers, GG, and Buffenstein, R. Acute appetite reduction associated with an increased frequency of eating in obese males. Int. J. Obes. Relat. Metab. Disord. 23: 1151-1159, 1999.
17. Stote, KS, Baer, DJ, Spears, K, Paul, DR, Harris, GK, Rumpler, WV, Strycula, P, Najjar, SS, Ferrucci, L, Ingram, DK, Longo, DL, and Mattson, MP. A controlled trial of reduced meal frequency without caloric restriction in healthy, normal-weight, middle-aged adults. Am. J. Clin. Nutr. 85: 981-988, 2007.
18. Taylor, MA, and Garrow, JS. Compared with nibbling, neither gorging nor a morning fast affect short-term energy balance in obese patients in a chamber calorimeter. Int. J. Obes. Relat. Metab. Disord. 25: 519-528, 2001.
19. Verboeket-van de Venne, WP, and Westerterp, KR. Influence of the feeding frequency on nutrient utilization in man: consequences for energy metabolism. Eur. J. Clin. Nutr. 45: 161-169, 1991.