Diets with a lower fiber intake and caloric density appear superior for weight loss.
Little is known about the effects of low caloric density diets on weight loss and maintenance. It makes sense that a diet that is lower in calories and higher in fiber will result in weight loss because lower density should result in lower calories per volume eaten. Diets are often designed to meet prescribed macronutrient targets. An example would be a high-protein diet which often suggests a protein intake of over 40%. The question persists as to whether individuals can actually achieve the specified levels and if they will result in weight loss.
A recent study used the data from the POUNDS LOST study to answer the question of which dietary pattern is most effective for weight loss. The POUNDS LOST study was a randomized clinical trial which examined the effects of four calorie-restricted diets of varying macronutrient composition on weight loss in free-living adults with obesity. The objective of this analysis was to identify predictors of weight loss after six months in participants who adhered to energy and macronutrient assignments. The subjects were analyzed to determine if they adhered to the energy restriction that should result in weight loss and if they stayed within the required macronutrient goals. Energy adherence was defined as consuming within 10% of the target energy goal. Diet adherence was defined as consuming within 5% of the target macronutrient composition for fat and protein.
Participants In the study were randomized to receive one of four diets. The groups were: 1) 20% fat, 15% protein (low-fat, average-protein), 20% fat, 25% protein (low-fat, high-protein), 40% fat, 15% protein (high-fat, average-protein), and 40% fat, 25% protein (high-fat, high-protein). Out of the 345 participants, only 46 met the criteria for adherence. The results revealed that the strongest predictor of weight change being dietary fiber and that a 10g increase in dietary fiber consumption was associated with an average of 8.1 pounds of weight loss. The fiber effect was independent of energy density and type of diet. Also, a decrease in energy density was positively associated with weight change for each diet-type, and this effect was most profound in the high-fat, average-protein diet.
The results of this study should really not surprise you. I have written another article on it and the result are consistent with the prior article (Research: Energy Density May Play a Part in Weight Loss). Yet another study from 2018 found that low energy density meals improve appetite control in women attempting weight loss and the effect is sustainable. Consumption of these lower energy density meals will likely contribute to weight loss.
The bottom line: These results suggest that dietary factors such a fiber content and lower energy density/caloric density may positively influence weight loss. Macronutrient composition also appears to be a fact, but only after fiber and calorie content/density. This finding is likely true because less dense foods should result in fullness and satiety at a similar volume and this a lower caloric level. More research is needed, but this study clearly indicates that we should all eat more fiber.