Effects of two weeks' mandatory snack consumption on energy intake and energy balance

Objective: Our goal was to compare the effects of mandatory consumption of commercial snack products (CSPs) on energy intakes and energy balance in free-living adults and to assess the interaction between habitual level of CSP consumption and the interventions.

Research Methods and Procedures: Four groups of 18 subjects (lean and overweight, males and females) were studied using a crossover design. Subjects consumed one type of CSP (high-carbohydrate, high-fat, or mixed composition) at three manipulations of energy 0 MJ (control), 1.5 MJ (low-energy), and 3.0 MJ (high-energy) each day during three 14-day interventions. The study design was parallel for type of CSP (macronutrient composition) and within-subjects for energy level. Subjects self-recorded food intakes between Days 8 and 14, and body weights were investigator-recorded on Days 1, 8, and 15 of each intervention period. Daily energy expenditure was estimated by heart rate monitoring.

Results: Daily energy intakes increased from 10.4 MJ (control) to 11.1 MJ (low-energy) and 11.5 MJ (high-energy) (p < 0.001), resulting in a trend (not significant) for body weight gain. Energy balance was more positive when subjects were not recording their food intakes than when they were (p < 0.001). There was a trend (not significant) for greater increases in energy intake with increasing fat content, and energy density, of the interventions. Frequent CSP consumers compensated more for the interventions than did infrequent CSP consumers (R2 = 0.125, p = 0.003).

Discussion: Subjects partially compensated for energy when supplemented with CSPs over 14-day periods, although this was insufficient to prevent some increase in energy balance. The level of compensation correlated with habitual energy intake from CSPs.