The purpose of this study is to observe the influence of carbohydrate-to-fat balance on liking, wanting and food consumption in humans.

16 normal-weight men (age: 23 ± 3 y)had completed a randomized 4-condition crossover study. The sessions differed by the composition of the breakfast which was rich in carbohydrates (HCB), low in carbohydrates (LCB), rich in fat (HFB) and low in fat (LFB). The HCB and HFB contained 2072 kJ, while the LCB and LFB contained 565 kJ. Two hours and 20 min later, energy expenditure (EE) and respiratory quotient (RQ) were measured before olfactory liking for 4 foods items and then ad libitum energy intake (EI) during a snack (sweet and fatty toast) were evaluated.

In accordance with the carbohydrate-based models of feeding, one may expect that food choices as well as "liking" and "wanting" (the two components of the reward system) could be influenced by glycogen stores and the carbohydrate-to-fat balance. More precisely, one may expect that a high fat oxidation rate could increase liking and wanting carbohydrates to replenish glycogen stores and conversely, that a high carbohydrate oxidation rate could produce the reverse. In order to validate this hypothesis, the present study has been conducted to investigate in humans the influence of the carbohydrate-to-fat oxidation ratio on carbohydrate-to-fat selection and the food reward system.

Inclusion Criteria:

• Good health
• Absence of medication
• Moderate physical activity (irregular and less than 5 h/wk)
• Low-smoking habit (less than 5 cigarettes/d)
• Normal body mass index (20< BMI <25)

Exclusion Criteria:

• Eating disorders
• Dieting or fasting
• Aversions for the foods offered and elevated 'cognitive restriction of eating' (score ≥ 7) according to the Three Factor Eating Questionnaire