Here's what you need to know...
- Research doesn't support the idea that eating more frequently "stokes the metabolic furnace."
- There's evidence that eating multiple small meals can increase protein synthesis, but this has only been shown in cases where protein intake is very low.
- It's best to experiment with different meal frequencies and see what works best for you. Above all, choose a frequency of feeding that fits your lifestyle.
You've heard the claims that eating small, frequent meals is the key to getting jacked. It speeds up the metabolism, satisfies hunger, and promotes better glucose control – a body comp homerun. At least that's what gym lore would have you believe.
Does the evidence support the practice of spreading out meals over the course of a day? Let's look at the research.
Proponents of eating frequent meals claim that it helps to "stoke the metabolic furnace." This is based on the set point theory, which dictates that your body strives to maintain enough energy (i.e., body fat) to survive the next famine. So when you go without eating for more than a few hours, the body senses deprivation and shifts into "starvation mode," and part of the starvation response is to decrease resting energy expenditure. In effect, the body slows down its metabolic rate to conserve energy.
While such claims may sound logical on the surface, there's scant evidence to support that it actually occurs. LeBlanc et al. (1) found that feeding dogs four small meals doubled the thermogenic response compared to eating the same number of total calories as a large single meal. A follow-up study by the same researchers found that humans also experienced heightened thermogenesis with more frequent feedings (2).
On the other hand, many other studies have failed to show that meal frequency has a tangible effect on energy expenditure (3-7). The body of evidence simply doesn't support any increases in metabolism as a result of partitioning nutrient intake over multiple meals.
Basic logic would argue against any enhanced effect of eating frequently on dietary thermogenesis. Thermogenic enhancements from frequent meals are commonly attributed to the thermic effect of food (TEF).
Simply, the TEF is the energy expended as heat resulting from the digestion of food sources. The various macronutrients have differing thermic effects, with protein causing the greatest energy expenditure and fat the least. The TEF of a typical mixed meal is estimated to be around 10% of calories consumed.
With this as background, let's take a look at how spreading out meals would affect the TEF in a 2400 calorie-a-day diet. If you ate three 800-calorie meals, the TEF would be 80 calories per meal. Multiply this by the number of daily meals (three) and you'll arrive at a total TEF of 240 calories.
Now if you were to consume that same 2400-calorie diet over six meals, the TEF would be 40 calories per meal. Do the math and you'll wind up with the same additional 240 calories burned as in the three-meal-a-day diet. Assuming macronutrient content and total calories remain constant, there is no difference in thermogenesis! The tables below illustrate this concept.
Table 1: 2400 Calories as Three Daily Meals
Table 2: 2400 Calories as Six Daily Meals
Appetite and Hunger
Proponents of frequent meals often claim that it helps to control appetite and hunger. It's well documented that weight management is primarily 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.
It's postulated that there's a tendency towards hypoglycemia (low blood sugar) during the lengthy post-prandial periods associated with infrequent meals. In an attempt to restore blood sugar, your body signals the hypothalamus that it needs food, especially simple carbohydrates. Hunger pangs ensue and you invariably end up eating more than you otherwise would, often as refined sweets. This sets up the vicious cycle of overeating and uncontrolled insulin secretions – a surefire route to unwanted weight gain.
However, research doesn't appear to support these lofty claims either. While a few studies have reported that subjects weren't as hungry when meals were spaced out over the course of a day (8-11), others have failed to detect differences on indices of appetite and hunger regardless of feeding frequency (12, 13).
In fact, some studies have found that eating three as opposed to six daily meals actually promotes greater feelings of satiety (6, 14). What's more, evidence is conflicting for how the number of meals consumed affects hunger-related hormones (13, 15). Taken as a whole, the belief that it's more satisfying to spread out nutrient intake is at best equivocal and likely related to individual factors.
Another claim often cited to support spreading meals throughout the day is that it has an "insulin-friendly" effect. According to the hypothesis, eating a few large meals causes a surge in blood sugar, which in turn leads to a spike in insulin levels. Given its role as a storage hormone, the bigger insulin peaks switch on mechanisms that increase fat deposition. Sounds ominous, but the validity of such claims are at best shaky.
A number of studies have shown that consuming more frequent meals produces a favorable effect on glucose homeostasis (16-20). This invariably translates into reduced insulin spikes and lower mean insulin concentrations. But the overriding question here is, do these findings matter? From a fat loss standpoint, the answer appears to be not really.
Munsters et al. (21) found that while frequent meals produced significantly lower peaks and more even glucose and insulin values compared with fewer feedings, there was no difference in fat oxidation between groups. Simply, both eating patterns resulted in the same amount of fat burned.
This study was noteworthy for its tightly controlled methodology. The researchers employed a crossover design where the same subjects consumed both diets and the exact same types and amounts of food. What's more, the subjects were lean, healthy adults, thereby more relevant to those who regularly work out.
The bottom line is that those who focus on the insulinemic effects on fat loss/accumulation in a healthy population have their eye on the wrong prize – the enemy is excess calories, not insulin.
Evaluating the acute effects of frequent meals can provide interesting clues as to potential ramifications of such an approach. However, the only thing that ultimately matters is whether eating more frequently improves body composition. This is where things get kind of tricky.
The study most often cited by frequent meal proponents involved competitive boxers who were placed on a 1200-calorie diet for two weeks (22). One group consumed the calories as two daily meals while the other group spaced out eating over six times a day.
At study's end, the frequent feeding group retained a greater amount of lean body mass compared to the two-meal-a-day group with similar total weight loss between groups. While these findings are intriguing, it must be noted that the study period was very short. Whether such results would continue over the long-term is speculative.
What's more, total protein intake amounted to just 60 grams a day – an amount far below what any hard-training athlete would require to prevent muscle catabolism. These limitations make it difficult to draw any firm conclusions on the topic.
A recent study by Arciero et al. (23) seems to further support a greater daily meal frequency. Briefly, the study employed an intricate design where two of the groups consumed a high-protein diet amounting to 35% of total calories of either three or six meals-a-day for approximately two months. Both groups showed approximately the same amount of fat loss (2.5 kilograms for the three meals versus 2.7 kilograms for the six meals). No biggie here.
However, the group who consumed frequent meals actually gained lean body mass (0.6 kilograms), versus a loss of LBM in the group that ate three daily meals (-0.9 kilograms). That equates to about 3 pounds of LBM – certainly nothing to sneeze at.
Again, results need to be taken with a grain of salt. In this case, subjects were overweight women who didn't participate in any regimented exercise, never mind an intense resistance training program. Whether similar results would be seen in serious lifters is anyone's guess.
What's more, it seems curious that frequency would have such a stark impact on lean mass increases given that the anabolic effects of protein consumption have been shown to last for up to six hours (24). This raises doubts as to the validity of the body composition measurements in this study.
In opposition to the aforementioned findings, a number of other studies have shown no body composition benefits to consuming more frequent meals (13, 25). In fact, a well-controlled randomized crossover trial by Stote et al. (8) found that a group of normal-weight middle-aged adults lost more body fat following a one-meal-a-day regimen compared to eating the same number of calories spaced out over three daily meals.
Take Home Points
So what can we infer from the research on meal frequency?
- The claims of "stoking the metabolic furnace" by spreading meals throughout the day are wildly overstated. At best, research on the topic is highly discrepant, leaving more questions than answers.
- There's some evidence that eating multiple small meals can have a positive impact on increasing protein synthesis (22, 26, 27), but this has only been shown in cases where protein intake is very low (at or below RDA guidelines). It's highly speculative whether these findings hold true when consuming the recommended levels of protein for a hard-training lifter (>1.6 grams/ kilograms).
- If you're a bodybuilder looking to win a show, even small improvements in body composition can be the difference between winning and losing a competition. So if your goal is to reduce body fat levels as low as possible while retaining muscle, then the best advice is to experiment with different meal frequencies and see what works best for you. Individual variation always has an impact on optimal results.
So choose a frequency of feeding that fits your lifestyle. If you like the regimentation of eating frequently throughout the day, then go for it. On the other hand, if you prefer consuming just a few large daily meals, that's a viable option as well. Just be consistent in your approach – there's some evidence that irregular eating patterns may negatively alter metabolic function (28, 29).
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