Identifying strategies to reduce energy intake and enhance satiety at meals is important for effective weight management. One strategy that may affect energy intake is changing the form in which food is consumed (solid, pureed, or liquid). While the literature on this topic is inconclusive, several studies have suggested that solid foods have a greater effect on satiety than liquids consumed as beverages^1-3. Fruit is particularly useful for investigating the effects of food form on satiety, because it is readily available in different forms.

This study had aims:

1. to determine whether food served in different forms affects satiety and energy intake independent of variations in Energy density or fiber content.
2. to determine whether consumption of fruit, which is low in energy density, affects satiety and energy intake at a meal.

Testing the effects of different forms of fruit on satiety

Fifty-eight adults, ages 18-45 years with a body mass index of 18-40 kg/m², were recruited for this study. Subjects came to the laboratory for breakfast and lunch once a week for five weeks. At the beginning of each lunch meal, subjects were served one of four preloads (apple, applesauce, and apple juice with and without Added fiber) or no preload. At the start of the meal, the preload was served and subjects were instructed to consume the entire food or beverage. They were then served a lunch meal, and were instructed to eat and drink as much or as little as they wanted. All foods and beverages were weighed before and after being served to subjects to determine the amount consumed. Subjects also rated their hunger, fullness, and thirst. All preloads were apple-based and were matched for weight (266g) and energy content (~125 kcal), but each differed in form. The apple preload consisted of peeled apples cut into segments. The applesauce preload was prepared by baking apples and then pureeing them to produce applesauce. The apple juice preload was commercially made from freshly pressed apples and contained no added sugar and no measurable fiber. The apple juice with fiber preload consisted of the same type of apple juice combined with an apple-derived pectin supplement.

Whole apple was the most satiating form of fruit

Results showed that eating apple reduced lunch energy intake (preload + test meal) by 15% (187 kcal) compared to control (p<0.0001). Consuming apple also significantly reduced total energy intake at lunch by 91 kcal compared to applesauce, by 152 kcal compared to apple juice with fiber, and by 178 kcal compared to apple juice without fiber (all p<0.02). Lunch intake was significantly lower when applesauce was consumed compared to both types of apple juice (p<0.05); in the two juice conditions, however, total energy intakes at lunch did not differ significantly from each other.

Hunger and fullness ratings differed significantly after preload consumption (apple>applesauce>both juices>control). Ratings of thirst were significantly lower following intake of apple and both juices compared to control, applesauce, and apple (p<0.001).

Fruit, energy density, and management of Energy intake and weight

This study builds on previous research shows that consuming whole fruit before a meal can enhance satiety and reduce subsequent food intake, leading to a substantial reduction in total energy intake at the meal.

There are number of reasons that have been proposed to explain the greater effect on satiety of whole fruit compared with juice. One possibility is the low fiber content of juice, although we did not find that adding fiber affected satiety Following juice consumption⁴. It is also possible that subjects perceived the beverages to be more effective at reducing thirst, while they expected the apple segments and applesauce to satisfy hunger, leading to differences in food intake and satiety⁵. Different forms of fruit may also have different effects on satiety due to intrinsic structural properties that affect volume and chewing. However, more research is needed to explore how differences in fiber, cognition, volume, and chewing interact to affect food intake and satiety when different forms of fruit are consumed.

Fruit consumption has also been associated with diets lower in energy density⁶, and research has shown that consuming a diet lower in energy density is related to reduced energy intake and body weight⁷. However, more research is needed to test the effects of consuming different forms of fruit on weight management. This study adds to the research suggesting that starting a meal with a low-energy-dense food, such as soup, salad, or whole fruit, reduces energy intake at the meal.

Funding Source: National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases, DK039177