The traditional weight loss strategy for the past 100 years has focused mainly on how much people were eating rather than on what they were eating. This led to recommendations to reduce portion sizes and/or use willpower to override hunger in an attempt to restrict calorie intake in order to create a negative calorie balance and reduce fat stores. Typically the calorie restricted diet was accompanied by recommendations to also increase calories burned via exercise. From the point of view of physics it seemed rational enough that excessive energy stores (largely body fat) could be reduced by consciously restricting calorie intake and consciously increasing calories burned. However, this approach has met with limited long-term success as witnessed by the fact that few people can continue using willpower to limit calorie intake over time. Indeed, it is clear that this strategy fails most of the time because, while more Americans are going on diet and exercise programs, there has been a steady rise in the average American’s BMI. In fact, roughly two-thirds of adults and a growing proportion of children are now overweight or obese. Clearly there is more to long-term weight control than using willpower to limit calorie intake and increase calories burned.
While the physics of energy balance are simple enough, there is now growing evidence that human beings, like other mammals, are biologically programmed to become less active in the face of limited energy intake and chronic hunger. And asking people to live with chronic hunger by consciously restricting their food intake creates an unresolvable conflict between the hunger drive and the intellectual will to eat less. Growing evidence also suggests that this unresolvable conflict plays a major role in the development of eating disorders. So researchers are now shifting their focus away from counting and consciously limiting calorie intake and encouraging exercise to focus more on what is being eaten (or not eaten) so that people can maintain satiety (or keep hunger at bay) at a lower calorie cost. One of the best-documented ways of reducing calorie intake without triggering increased hunger is to reduce the calorie or energy density (ED) of the foods consumed.
There are many ways to reduce the ED of a meal. Three of the most common include reducing the amount of fat (as fat is by far more ED than sugar, starch, or protein), increasing the water content of foods (as opposed to simply drinking it with a meal), and increasing the intake of foods that are naturally less calorie dense, like whole fruits and vegetables. To study the efficacy of these three methods of reducing ED to reduce ad libitum calorie intake, Dr. Rolls and associates recruited a group of healthy subjects who were not on a calorie-restricted diet, smokers, athletes in training, or on drugs that could impact appetite. A total of 62 subjects started the study (and 59 of them completed the study). ED was reduced by 20% using one of the three methods -- decreased fat, increased water content, or increased fruit and vegetable (F&V) content of the main entrees served at breakfast, lunch, and dinner. This was a crossover design, with each subject following each of the three ED reduction methods and one control day with no ED reduction in random order over a four-week period. On the test day, subjects were fed either the standard meal or the same entrée, altered so that ED was reduced by 20% using one of the three different strategies. The reduction in fat content was accomplished by simply adding less fat to the main entrees served at breakfast lunch, and dinner. Increased fruit in the breakfast and increased vegetables added to the lunch and dinner entrees reduced ED 20% on the increased F&V day. And increased water was added to the main entrees, reducing ED by 20% compared to the control day. Entrée portion sizes were large enough so subjects could consume as much as desired of the test meals. Leftovers were weighed to determine precisely how much was consumed on each of the test meals. The average reduction in ad libitum energy intake was 396kcal, 308kcal, and 230kcal on the days the ED was reduced 20% via reduced fat, increased F&V, and increased added water, respectively. The average calorie intake was reduced by 15, 11, and 9% compared to the control day (with no ED reduction). The energy content of the manipulated entrees accounted for two thirds of total energy intake on the test days. While the spontaneous reduction in ad libitum calorie intake was significantly lower using all three strategies to reduce ED, it should be noted that the reduction in calorie intake was significantly greater with fat reduction than with either increased F&V or increased water content. It should also be noted that the subjects reported no differences in hunger or satiety ratings on on all three days when ED was significantly reduced, suggesting that reducing ED may be an effective strategy for reducing calorie intake without any need to use willpower to try to overcome the increased hunger levels that accompany traditional calorie-restricted diet plans that involve subjects using willpower to restrain the amount of food eaten. [Williams RA, Roe LS, Rolls BJ. Comparison of three methods to reduce energy density. Effects on daily energy intake. Appetite 2013;66:75-83].
Bottom Line: While this study showed that reducing the amount of fat added to foods was the single most effective way to reduce ad libitum calorie intake, it is clear than all three strategies are effective. Furthermore, these three strategies are not mutually exclusive, so it is likely that using all three in combination would likely work even better than each one alone. A breakfast oatmeal entrée could have its ED reduced by increasing the amount of berries added to the oatmeal, increasing the amount of water used to cook the oatmeal, and by eliminating the added butter or margarine. It should also be noted that yet another strategy not used in this study but validated in others would be replacing calorie-dense brown sugar or maple syrup with Splenda or sugar-free maple syrup. This would further reduce the ED of this breakfast entrée.
By James J. Kenney, PhD, FACN
Stephanie Ronco has been editing in a professional capacity for the past 10 years. In addition to her work as an editor, Ronco has also served as a ghostwriter and writing tutor. A voracious reader, Ronco loves watching language evolve and change. When she’s not delving into her latest project, Ronco can be found teaching acting classes, performing in community theater, or sailing with her husband.