Summary
Worldwide, the number of overweight and obese individuals has more than doubled since 1980: there were more than 1.4 billion overweight adults in 2008. Of these, more than 200 million men and nearly 300 million women were classified as obese. The cause for the worldwide increase in the prevalence of obesity is unknown but it is most probably due to two lifestyle factors: an increasingly sedentary lifestyle and increased availability of palatable foods with high energy density. Even small changes in energy intake, leading to a positive energy balance can lead to weight gain over time. Therefore, slight modifications in food intake, such as the substitution by energy-reduced foods or foods that affect appetite and thereby reduce energy intake, may prevent weight gain and even facilitate weight loss.

The overall aim of this PhD project was to investigate whether substitution of an ingredient or a single food can affect appetite and reduce energy intake. Specific objectives were:
1. To compare the effects of sucrose versus artificial sweeteners on appetite sensations and ad libitum energy intake.
2. To compare the effect of the modified triacylglycerol salatrim versus traditional fat on appetite sensations, ad libitum energy intake and gastro-intestinal satiety hormones.
3. To compare the effect of dark chocolate versus milk chocolate on appetite sensations and ad libitum energy intake.

In paper 1, the participants who received sucrose supplements had lower ratings of fullness and higher ratings of prospective food consumption between lunch and dinner, and after dinner than the participants who received artificial sweetener supplements. Both groups had a high energy intake during the test day, but the sucrose supplements induced a higher energy intake, compared with the artificial sweetener supplements.

In paper 2, the modified triacylglycerol salatrim did not reduce energy intake, compared with traditional fat, despite slightly higher ratings of fullness during the salatrim test day. The slight difference in fullness was not due to differences in gastro-intestinal satiety hormones. The data 7 indicated that there was no difference in fat absorption after the two fat rich meals, although this was not measured directly.

In paper 3, higher ratings of satiety and lower ratings of hunger and prospective consumption were recorded after consumption of the dark chocolate than after the milk chocolate. Ratings of the desire to eat something sweet, salty, fatty, and savoury were all lower after consumption of the dark chocolate than after the milk chocolate. The results suggest that it could be beneficial to use dark chocolate as a substitute for milk chocolate.

In summary, these results suggest that substitution of specific ingredients and foods can affect appetite and reduce energy intake in the short term.