The Food Journal and Food, Nutrition & Science

An alliance between The Lempert Report and The Center for Food Integrity

Fruit and Fiber

Fruit and Fiber

Health and Wellness

February 24, 2008

Fruit and Fiber
A diet containing more than average amounts of fiber, complex carbohydrates and fruit is closely associated with the maintenance of normal weight and fat stores in the human body, according to a recent University of Southern California and University of Texas study. The study, which looked at 53 normal-weight adults and 52 overweight or obese adults, found that increasing one’s intake of fiber-rich foods, especially fruit, contributes to weight loss and management.
Although several studies in the past have analyzed the relationship between diet and body mass index (BMI) and body weight, few studies have looked at the influence of dietary habits on body fat percentages. The USC, UT study sought to understand the role that nutrition has in fat storage tendencies. They found that total dietary fiber intake, more than the intake of any other nutrients, is a negative predictor of percent body fat. Normal weight subjects consumed 33% more dietary fiber and 43% more complex carbohydrates daily than their overweight counterparts.
“Simply stated, fiber is the undigested portion of plants. Some types of fiber slow down gastric/stomach emptying time making the food ‘last longer.’ Stomachs, when full, secrete neuropeptides that turn off the appetite,” says Roberta Anding, spokesperson for the American Dietetic Association.
While overweight subjects consumed 38.7% of energy from fat, 18.1% from protein and 44.9% from carbohydrates, normal weight subjects consumed 33.5% of energy from fat, 17.2% from protein and 52% from carbohydrates. At first glance, this higher consumption of carbohydrates among normal weight subjects may appear confusing, especially in light of the popularity of low-carb diets and their negative effect on weight. However, when the carbs in question were complex carbs or carbs derived from dietary fiber, the subjects easily maintained a normal weight.
As a whole, overweight subjects did consume more total fat, saturated fat and cholesterol, as well as significantly less fiber than their normal weight counterparts. But total energy and protein intake did not differ significantly between the two groups. Consumption of bread, dairy and added sugars did not differ significantly either – a strange finding considering the attention paid to these factors, and their influence on the increasing obesity epidemic, in previous studies. Instead, diets low in servings of fruit and high in servings of meat (especially fattier meats) exerted greater influence on adiposity (the tendency to store fat) than any other factor.
“Those on low-carb, high protein diets might want to consider adding certain fiber-rich carbs, like fruits and vegetables, to their diet,” says Anding.
For the purpose of applying these results in a practical manner to weight management programs, the study took a closer look at the individual foods and food groups consumed. Individual fruit items, like apples and fresh, cut-up fruit, were inversely related to weight, BMI and percent body fat for the entire group. Obese subjects consumed, on average, one less fruit serving daily when compared to their normal weight counterparts. Normal weight subjects seemed to consume a higher percentage of daily sugars from fruit, while overweight subjects consumed a higher percentage of their daily sugars from baked products and sweets.
Interestingly, there is one factor that both groups have in common. Intake of grains was actually down for both normal weight and overweight subjects, slightly below the daily recommendations specified in the Food Guide Pyramid recommendations. Why? Media attention to the “negative” impact of carbs on weight may be influencing individuals to eat fewer grains overall, even when some of those grains may be high in fiber.
“They key is to eat foods closest to the way they come out of the ground, meaning as minimally processed as possible. Fruits, vegetables and plant-based foods should take center stage on any plate,” saying Anding.
In addition to curbing hunger, fiber helps promote health in other ways. Fiber helps lower cholesterol levels, normalize blood sugar levels, stabilize insulin levels, prevent constipation, and even helps in the prevention of certain cancers. Dietary fiber intake among adults in the United States averages about 15 grams. The Institute of Medicine recommends consuming 14 grams of fiber for every 1,000 calories you need – about double the U.S. average for fiber consumption.