Eating frequency and the prevalence of snacking in particular have increased in Western nations over the past 35 years. There is strong epidemiological evidence that there is a positive association between eating frequency and energy intake. However, whether this translates to an increase in BMI is less clear. With adjustment for underreporting, a major confounder in eating frequency outcomes, the sometimes reported negative association between eating frequency and BMI, is often reversed. Snacks are most problematic when they are unplanned and evoke weak compensation, contributing to increased energy intake. Mechanisms that contribute to this include a weak satiation/satiety effect, distracted eating, low thermogenic (heat production) response, and disrupted biological cycles. Although snacks are commonly energy dense, this attribute alone does not make them more problematic, as fruits and vegetables as snacks can also increase total energy intake. Thus, problems with snacks do not necessarily stem from the food themselves but rather how they are incorporated into a diet. Snacking as part of an energy balanced diet can help manage short time intervals allotted to eating, contribute positively to the nutrient quality of the diet, and may moderate blood sugar and metabolic disease risk factors.