Over the past 40 years, meal skipping and snacking in US adults have increased, and currently most eating occasions occur later in the day than previously. Whether these changes have played a causal role in the obesity epidemic is poorly understood. Observational studies are largely inconclusive due to methodological limitations. Experimental evidence does not support a causal role for eating frequency or breakfast skipping in weight control. Emerging evidence suggests that eating irregularity and eating later in the day may be detrimental for weight control, but more studies are needed. This article summarizes studies and highlights areas needing attention.