Two studies have examined the effect on energy intake and macronutrient selection of increasing increments of mandatory high-fat or high-sugar snacks into the diet in men. The present study used a within-subject, repeated-measures design. In each experiment, six lean and six overweight, unrestrained men were each studied over three 7 d treatment periods, during which they were given mandatory snacks of the same energy density (550 kJ/100 g) comprising the following (in terms of percentage energy as fat-carbohydrate-protein): high-fat, 80:10:10; high-sugar, 10:80:10, of which 65 % was sugar, and 15 % starch. Subjects were given 0, 1.5 or 3.0 MJ/d snacks, in a randomised counterbalanced design, to be consumed mid-morning and mid-afternoon. Throughout each day, subjects had access ad libitum to fifteen high-protein, fifteen high-fat and fifteen high-carbohydrate foods, rotated on a 3 d menu. Mandatory high-fat snacks significantly elevated energy intake and fat intake, whereas high-sugar snacks elevated energy intake and carbohydrate intake (all P<0.02). Mandatory increases in sugar intake did not displace fat from the diet or vice versa. It was concluded that the ingestion of up to 3 MJ/d high-fat and high-sugar foods promoted weak compensation (18 % and 30 %, respectively) and therefore elevated daily energy intake by approximately 2.0-2.5 MJ.