Snacking, like any dietary behavior, can be practiced in a manner that is healthful or not. The case presented in this critical review of the literature is that snacking is problematic, primarily due to its contribution to positive energy balance and promotion of overweight/obesity. There is strong evidence that snacking is associated with greater energy intake. How this translates to body weight is less clear, largely due to limitations of experimental measurement tools and research designs. Correction for these shortcomings reveals evidence implicating snacking in the high prevalence of overweight/obesity supported by multiple plausible mechanisms. Given the popularity of snacking and its potential to positively contribute to diet quality, it is recommended that efforts be made to better understand and harness snacking to a better purpose.