Meal Patterns Appetite and Energy Balance

The effect of meal patterns on appetite and energy balance is also an unresolved issue. It has been noted that snacking and commercially available snack food are often believed to elevate EI. However, there is considerably less evidence that meal or snack patterns contribute to the development of obesity. It is important to note at this point that the relationship between a meal and a snack relates to timing and size of ingestive events in meal-feeding animals. In nonhuman species (and indeed humans) who engage in numerous small feeding bouts throughout their diurnal cycle there is little if any distinction between a meal and a snack. Meal-feeding animals are conditioned to ingest the majority of their EI in a few large ingestive events in their diurnal cycle, at approximately the same time points. Under these conditions, a snack can be defined as an energetically small, intermeal ingestive event (SIMIE). To avoid confusion with a common use of the word to describe a certain type of commercially available food, we use the phrase 'commercially available snack foods' to describe those specific foods. Commercially available snack foods tend to differ from the rest of the diet as they are more energy dense, high in fat and carbohydrate and low in protein, and usually contain a large fraction of their edible mass as dry matter. They are by no means the only food eaten as a SIMIE in many people at large.

There are two alternative hypotheses about how snacking may influence EI and body weight: (1) snacking helps 'fine tune' meal-time EI to match intake with requirements; or (2) habitual consumption of calorific drinks and snacks between meals is a major factor driving EI up and predisposing people to weight gain and obesity.

The evidence in relation to meal patterns, appetite, EI, and body weight is, however, indirect and fragmentary. On aggregate, cross-sectional studies tend to support no or a negative relationship between meal frequency and BMI. However, Bellisle et al. (1991) convincingly argue that examinations of the relationship between snacking and energy balance in free-living subjects are extensively flawed by misreporting, misclassification of meals and snacks, and potentially by reverse causality. Under these conditions it is difficult to draw clear conclusions about the effects of snacking in cross-sectional studies. It is therefore important to conduct controlled laboratory interventions over a number of days in humans. These studies suggest that in the short to medium term adding mandatory snacks to the diet leads to overconsumption. This effect is most pronounced in those who do not habitually snack and least pronounced in those who do. It is also of note that rats tend to be 'snackers' and Western humans tend to be meal feeders. The rat tends to adjust EI by varying meal frequency, the human by varying meal size. However, if rats are meal fed, they learn to adjust EI by varying meal size. Humans placed in time isolation begin to adjust intake by varying meal frequency. These comparisons illustrate the fact that adjustment of intake to energy or nutrient requirements occurs within a conditioned time framework, which itself is variable depending on the conditioning environment. Despite large changes in the pattern of feeding, EI can still be adjusted to satisfy requirements.

The Mediterranean Diet Meltdown

The Mediterranean Diet Meltdown

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