Latest Research: Quantity Not Key, Whole Food Diet Helps You Eat More, Consume Fewer Calories

As the initial burst of New Year’s motivation fades, many people find themselves struggling with weight management and the constant battle to ‘eat less.’ But what if the key to lasting weight and metabolic health isn’t about portion control and willpower, but about the quality of your food? Latest nutritional research proposes a counter-intuitive view: increasing the quantity of food you eat does not mean consuming more calories. The true secret to sustained weight management and metabolism lies in the degree of food processing.

Whole Food Diet: 57% Increase in Volume, 300 Fewer Calories

A British study¹ published at the end of December re-analyzed data from a randomized feeding trial originally published by NIH researchers in 2019. The data involved 20 adults who participated in two weeks of “ultra-processed diet” and two weeks of “unprocessed diet,” crossing over afterward. Participants could eat freely in both phases, with no calorie or portion limits.

Researchers observed the impact of food processing levels on eating behavior. The results showed:

1. Increased Quantity, Lower Calories: When eating the unprocessed diet, the average food weight was about 57% higher, and the plate looked fuller. However, the total daily calorie intake was an average of 300 to 330 calories lower.
2. Energy Density Difference: The unprocessed diet averaged 719 calories per meal, while the ultra-processed diet averaged 829 calories. The difference stems from the variation in energy density.
3. Source of Low-Calorie Volume: The extra volume in the unprocessed diet mainly came from high-water, low-calorie foods like vegetables and fruits.
4. High Energy Density Trap: Ultra-processed foods are rich in refined starches, added fats, and sugars. Even in small portions, energy is highly concentrated, leading people to consume excessive calories before feeling full.

The “Nutritional Wisdom” of Food Choices

The re-analysis also showed that participants in the unprocessed diet phase naturally chose foods with lower energy density, fewer fats and refined carbohydrates, and significantly increased vegetable and fruit intake. The research team called this phenomenon “Nutritional Wisdom,” referring to our ability to better balance micronutrient needs and energy intake when faced with whole foods.

This aligns with the original 2019 study², which found that participants consuming the ultra-processed diet consumed about 500 extra calories per day on average and experienced weight gain, while EatClean dieters lost weight without deliberate dieting.

Five Practical Recommendations From A Dietitian

The data consistently shows that fat loss is not just a matter of quantity, but a matter of food structure and/or processing.

1. Increase Low Energy Density Foods: No need to deliberately reduce portion sizes; instead, increase the proportion of low energy density foods like vegetables, mushrooms, and fruits. This allows you to eat more while controlling total calories.
2. Ensure Adequate Protein: Each meal should include a source of protein such as fish, eggs, tofu, legumes, or meat. Protein helps prolong satiety and prevents blood sugar fluctuations that lead to premature hunger.
3. Choose Whole Grains: Replace refined starches like instant noodles and biscuits with whole forms like brown rice, oats, sweet potatoes, or whole grains to boost fiber and micronutrient intake.
4. Be Wary of High-Calorie Drinks and Snacks: Packaged snacks and added-sugar drinks (foods that are “quick to eat but don’t feel filling”) have concentrated energy but low satiety and should be treated as occasional choices.
5. Focus on the Proportion of Processed Foods: Instead of fixating on calorie counts, examine the proportion of processed foods in your daily diet. When the diet reverts to whole foods, food intake will self-regulate without the need for deliberate dieting.

1. Brunstrom, Jeffrey M., et al. “Consuming an Unprocessed Diet Reduces Energy Intake.” The American Journal of Clinical Nutrition, Dec. 29, 2025, https://ajcn.nutrition.org/article/S0002-9165(25)00775-0/fulltext
2. Hall, Kevin D., et al. “Ultra-Processed Diets Cause Excess Calorie Intake and Weight Gain.” Cell Metabolism, vol. 30, no. 1, 2019, pp. 67–77.e3, https://www.cell.com/cell-metabolism/fulltext/S1550-4131(19)30248-7