It seems that one of the most obvious disadvantages with irregular meals is the increase of insulin resistance which can lead to type 2 diabetes.
The effect of the timing of food intake on metabolism has been the subject of active investigation for >40 y. Indeed, whether it is "better" to eat many small meals a day is one of the questions most frequently posed by the lay public. Comparing the potential benefits of nibbling and of gorging has been the focus of much animal and human research, but no clear consensus has emerged (1-7). Simply put, the question of whether there is a health benefit from the consumption of multiple small meals will ultimately depend on how much energy is consumed, as opposed to how often or how regularly one eats. This possibility raises 2 questions. First, is it easier to overeat under a regimen of frequent, irregular meals? Second, how does the pattern of meal consumption affect metabolic health?
As shown by Farshchi et al, the regular eating frequency was associated with lower reported ad libitum energy intakes and lower fasting total and LDL-cholesterol concentrations. In addition, they concluded that the irregular eating frequency may have reduced insulin sensitivity because that pattern was associated with a lower thermic effect of food (TEF), a higher peak insulin concentration, and a larger 3-h area under the curve of postprandial insulin concentrations. One practical limitation of the work by Farshchi et al is that each dietary phase was only 14 d long and thus did not result in large effects (eg, an ≈9% greater peak postprandial insulin concentration and an 8% lower TEF).
Two last issues raised by Farshchi et al (8) are whether the effects on metabolism of eating regularity are independent of or mediated by energy intake, and, if there are independent effects, what mechanisms contribute to these effects. With respect to insulin resistance, endocrinologists have long known that, when diabetics are hospitalized for observation, they have significant improvements in blood glucose and insulin concentrations—an effect partially caused by the consumption of regular balanced meals (19). Yet the exact mechanism supporting improved insulin response is unknown.
There were no significant differences in body weight and 3-day mean energy intake between the regular and irregular meal pattern. In the irregular period, the mean energy intake on the day when 9 meals were eaten was significantly greater than when 6 or 3 meals were consumed (P=0.0001). There was no significant difference between the 3 days of the regular meal pattern. Subjective appetite measurement showed no significant differences before and after the test meal in all visits. Fasting RMR showed no significant differences over the experiment. The overall thermic effect of food (TEF) over the 3 h after the test meal was significantly lower after the irregular meal pattern (P=0.003).
Irregular meal frequency led to a lower postprandial energy expenditure compared with the regular meal frequency, while the mean energy intake was not significantly different between the two. The reduced TEF with the irregular meal frequency may lead to weight gain in the long term.