The key is that fruits and vegetables have a low calorie density, explains research studies from Pennsylvania State University.1 Low-calorie-dense foods are full of water and fiber, making them big and heavy and therefore filling, but they don’t add a lot of calories to the diet.
Analyzing 658 overweight hypertensive men and women, all of whom were attempting to shed weight over a six-month period, lead author Jenny Ledikwe, PhD, and colleagues found that those with the greatest reductions in the calorie density of their diets lost the most weight, an average of 13 pounds. Those who made the smallest reductions in calorie density lost the least amount of weight, averaging just 5 pounds.
Though they shed the most weight, the low-calorie-dense eaters ate the most food – “and the greatest increases in both fruit and vegetable intake,” noted the authors, which “may have helped to control feelings of hunger and to promote feelings of satiety while reducing energy [calorie] intakes.”
An additional benefit of adopting a low-calorie-dense diet was a healthier diet. The men and women with the greatest decreases in the calorie density of their diet had the highest increases in fiber intake, the highest increases in intakes of many vitamins and minerals, and the greatest decreases in fat and saturated fat intake. They also ended up with the best blood pressure readings.
At the start of the study, the subjects were divided into three different diet groups. The first group received a single 30-minute session on general lifestyle tips to improve health.
The other two groups attended 18 sessions (14 group meetings and 4 individual counseling sessions) over six months. The first group was taught to cut calories by adding 9 to 12 daily servings of fruits and vegetables and 2 to 3 servings of low-fat dairy foods, also known as the DASH diet (Dietary Approaches to Stop Hypertension). The second group was simply told to cut calories.
Fruits and vegetables
Overall, the scientists found that the DASH group cut down the most on calorie density, and the DASH dieters who ate the greatest number of fruits and vegetables shed the most weight of all the other dieters.
In summary, wrote Dr. Ledikwe and team, “participants with diet patterns characterized by the largest decrease in the energy [calorie] density had the greatest decrease in calorie intake and the largest declines in body weight. Even modest reductions in calorie density that accompanied increased intakes of fruit, vegetables, fiber, vitamins, and minerals and of the total weight of food consumed were associated with reduced body weight.”
In related research, Dr. Ledikwe and others at Pennsylvania State University conducted a year-long trial comparing two weight-loss diets.2 Ninety-seven women were randomly assigned to either a diet group designed to reduce fat intake while increasing intake of water-rich foods, particularly fruit and vegetables, or a diet group that focused solely on reducing fat intake.
Both groups were instructed to eat as much as they wanted while following the principles of their diet.
“I’m not hungry anymore.”
After one year, both groups had significant decreases in body weight, averaging 17.5 pounds in the reduced fat/fruit and veggie group and 14 pounds in the reduced fat group, but the fruit and veggie eaters reported feeling less hungry and far more satisfied. Analysis showed they had consumed more food by weight each day – big filling portions for snacks as well as meals.
The authors concluded that “reducing dietary energy [calorie] density, particularly by combining fruit and vegetable intakes with decreased fat intake, is an effective strategy for managing body weight while controlling hunger.”
308 fewer calories each day
Recent research from Penn State has continued to affirm the value of pumping up our fruit and vegetable intake. Tracking 59 men and women between the ages of 20 and 45, lead researcher Barbara Rolls and colleagues found that those who ate fruits and/or vegetables with every snack and meal ended up consuming 308 fewer calories each day compared to their regular-eating days.3
Focus on what you eat (more fruit, veggies, and other whole, water-rich foods) rather than how much you eat. Doing so will just naturally allow you to eat more, weigh less, stay sane, and be successful long-term.
- 1 American Journal of Clinical Nutrition, 2007; 85: 1212.
- 2 American Journal of Clinical Nutrition, 2007; 85: 1465.
- 3 Appetite, 2013; 66: 75.