Low energy density foods keep you satisfied (and may help you lose weight)

We've written a great deal about energy density. To review: energy density refers to the overall number of calories by weight a food contains. A high energy density food contains more calories by weight: think of butter, for example, or chocolate as extreme examples. Small amounts of these foods contain more calories than similar amounts of low-energy-density foods like popcorn, lettuce, or celery.

Choosing to eat lower-energy-density foods would seem to be a good weight loss strategy: foods that are lower in energy density have greater volume than foods that are higher in energy density with the same number of calories. For example: 100 calories of popcorn are about 4 cups in volume, while 27 M&M's are also about 100 calories. Which do you think would be more satisfying?

It might seem obvious to you and me, but human appetite is more complex than simple volume. Some studies have suggested that low-energy-density diet plans might be satisfying for a while, but might lead to binging on forbidden higher-energy-density foods: in short, a low-energy-density diet might appear to be satisfying, but would lead to greater cravings and over the long term wouldn't contribute to weight loss.

A team of researchers in the UK sought to test whether a low-energy-density diet would be satisfying over the long term, and whether that might help with a weight loss program (J Nutr 2018;148(5):798-806).

In the UK and Ireland, a popular weight-loss group is known as Slimming World. Somewhat similar to Weight Watchers in the United States, Slimming World combines weekly meetings and weigh-ins with other behavioral change components to help its members effectively lose weight. Among the strategies it promotes are daily food diaries and weight records as well as the idea of "Food Optimizing," advocating nearly uncontrolled intake of many low energy density foods and controlled intake of higher energy density foods.

The authors sought to compare the results of Slimming World's low-energy-density approach with the National Health Services' standard of care: a "free, structured, self-led program [that] recommends a daily reduction of 600 kcal" in the context of increased physical activity as well as reducing overall caloric intake.

For their research, the authors recruited a total of 96 women, about half from newly signed up members of Slimming World and half from female members of the NHS who were not members of Slimming World but who sought to lose weight using the NHS program. All of the women were clinically overweight or obese but otherwise healthy and had no conditions that might affect weight loss, nor were they taking medications that might affect weight loss.

The study began with a two-week run-in period to allow the participants to get used to their meal plans. They were weighed, their body fat was measured, and blood was taken for standard health panels in the first two weeks and at the end of the program. During weeks 3 and 4 and then again in weeks 13 and 14 each participant spent two days in the lab consuming a low energy density set of meals (breakfast, lunch, dinner) on one day and a high energy density set of meals on the second day a week later (the order of high versus low energy density days was set randomly).

These test days were important because they were designed to assess whether low energy density meals were as satisfying as high energy density meals - and would that change if you were regularly consuming low energy density meals?

The breakfast and lunch meals on the test days contained the same number of calories (adjusted for the caloric needs of each participant) regardless of whether it was a high-calorie-density day or a low-calorie-density day. The authors only describe the breakfast meal as "a cooked breakfast with a sweet side dish," but the lunch description might give you a better idea of what the participants ate: it's described as "a baked potato meal with salad."

A medium plain baked potato contains about 150 calories: a high energy density meal might include plenty of butter and full-fat cheese for that baked potato with a higher calorie dressing on a smaller salad, while a lower-energy-density meal might put reduced-fat sour cream and plenty of sliced green onions on that baked potato, with a lower calorie dressing on a much larger salad.

For the evening meal the participants were served as much of a beef-based chili con carne as they wished to eat: the only difference being that one chili con carne recipe was low in energy density (for those on a low-energy-density test day) and one was high in energy density (for those on a high-energy density test day).

While the participants were required to consume all of their test breakfast and lunch meals, but they were allowed to eat as much or as little as they wished to eat of their evening meal. The authors assessed how much in terms of both weight and calories the participants consumed of those evening meals. Further, the authors assessed the participants' appetite before and after each meal.

After 14 weeks, those who were following the low-energy-density recommendations of Slimming World lost nearly twice as much weight (a total of almost 6% of their body weight) as those following the standard of care recommendations. Further, they reported being more satisfied with their weight loss program, felt it was easier to stick to, and felt more on control over theri eating than those on the standard of care program.

For those days in the lab, the authors were somewhat surprised to find that regardless of which diet people were following overall, they were less hungry, felt less of a desire to eat, and believed that they would eat less at every point during the low-energy-density meal days as compared to the high-energy-density days, except for when their appetite was tested before breakfast. In short: the low energy density meals were more satisfying than the high energy density meals. Further, on those low energy density days the participants consumed half the calories of the low energy density evening meals as compared to the high energy density meal. The overall number of calories the participants consumed on low energy density days averaged about 600 calories less than those consumed during high energy density days.

What this means for you

Foods that are lower in energy density are likely to be just as satisfying as foods that are higher in energy density, and consuming more of them are likely to help you lose weight. The good news is that foods that are lower in energy density tend to be foods that are great for you, like fruits; vegetables; legumes, nuts, and seeds; foods that are higher in fiber (like brown rice); and lean meats. In short, a Mediterranean style diet is a great way to eat more food by volume while consuming fewer calories and more vitamins, minerals, and nutrients.

First posted: May 9, 2018