Dietary manipulation and energy compensation: does the intermittent use of low-fat items in the diet reduce total energy intake in free-feeding lean men?

OBJECTIVE

The effect of two low-fat treatments on ad libitum energy intake (EI) was investigated in five lean men living within a metabolic facility.

DESIGN

Diet was controlled over two consecutive periods of 12 d when either, i) all foods eaten or ii) only a single (lunch) meal, was manipulated to increase the fat content from 20, 40 to 60% of energy, and ad libitum EI measured.

RESULTS

All foods: EI increased from 8.6 (2.9 s.d.)-14.8 (3.1 s.d.) MJ/d and energy density (ED) from 4.1 (0.8 s.d.)-7.7 (1.6 s.d.) kJ/g as fat content increased from 20-60% (P < 0.0001). There was no decrease in weight of food eaten across diets (P > 0.05) and hence no energy compensation. Lunch meal: EI (20%:13.1 MJ/d, 40%:13.8 MJ/d, 60%:14.8 MJ/d) and ED (6.03 kJ/g, 5.89 kJ/g, 6.41 kJ/g) increased but not significantly across treatments (P > 0.05). There was partial energy compensation on the low-fat 20% diet (due in part to compensatory increase in fat intake), but no compensation for the high-fat 60% diet.

CONCLUSIONS

Changes in total dietary fat and ED result in concomitant changes in EI; low fat diets reducing EI. However, the dietary strategy of intermittent use of low- and high-fat items fail to significantly alter ED, and hence EI, in free-feeding lean men. Whilst there is a trend towards reduction in intake, manipulation of the fat content of a single meal may not be sufficient to induce significant long-term weight loss.