Consuming an unprocessed diet reduces energy intake: a post-hoc analysis of a randomized controlled trial reveals a role for human nutritional intelligence

TL;DR

Eating an unprocessed diet leads to lower calorie intake, possibly because people choose more varied and lower-calorie foods.

Contribution

The study reveals that human nutritional intelligence influences meal choices and energy intake when consuming unprocessed diets.

Findings

Participants on an unprocessed diet selected meal components with less balanced energy from carbohydrates and fat.

Unprocessed meals were lower in energy but higher in mass compared to ultraprocessed meals.

Low-energy-dense mass and blend index strongly predict energy intake.

Abstract

In 2019, Hall et al. reported a randomized clinical trial showing that an ultraprocessed diet increases energy intake by ∼500 kcal/d compared with an unprocessed diet.

This post-hoc analysis assessed whether participants selected meal components with specific nutritional characteristics and how this affected energy intake.

Twenty weight-stable adults received an ad libitum ultraprocessed or unprocessed diet for 2 wk, followed by the alternate diet. ANOVA and t tests assessed diet effects; a linear mixed model assessed predictors of meal size.

With the unprocessed diet, participants selected components with a less-equal blend of energy from carbohydrate and fat [“blend index” difference; lunch = 0.22 (95% CI: 0.19, 0.26), P< 0.0001, d = 0.76; dinner = 0.24 (95% CI: 0.19, 0.28), P< 0.0001, d = 0.71]. These components formed meals that had a lower blend index (less balanced) than ultraprocessed meals [lunch, F(1, 19) = 18.49, P < 0.0004, partial η2 = 0.493; dinner, F(1, 19) = 24.85, P < 0.0001, partial η2 = 0.57]. With the unprocessed diet, participants preferentially chose low-energy-dense components (<1.0 kcal/g, mostly fruits and vegetables), creating meals lower in energy (unprocessed = 719.4 ± 11.6 kcal compared with ultraprocessed = 829.5 ± 12.51 kcal), [F(1,19) = 14.9, P < 0.001, η2G = 0.0457], yet significantly larger (57%) by mass (unprocessed = 665.5 ± 10.74 g compared with ultraprocessed = 423.5 ± 8.03 g), [F(1,19) = 82.9, P < 0.001, η2G = 0.274]. Modeled together, low-energy-dense mass and blend index strongly predict observed energy intakes (r = 0.78, df = 1676, P < 0.001).

Unprocessed meals may reduce energy intake because: 1) they have a less balanced carbohydrate-fat blend; and 2) they promote a form of nutritional intelligence whereby a compromise is struck between consuming calories and consuming micronutrients, which we refer to as “micronutrient deleveraging.”

This trial was registered at clinicaltrials.gov as NCT03407053.

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