Effect of a Phenotype-Tailored Lifestyle Intervention on Caloric Intake and Macronutrient Composition in Adults with Obesity: A Secondary Analysis of the PHENO-Diet Trial

Background/Objectives: A 12-week trial demonstrated that phenotype-tailored lifestyle intervention (PLI) was associated with greater weight loss than standard lifestyle intervention (SLI); however, differences in dietary patterns between groups were not examined. Methods: This secondary analysis evaluated caloric and macronutrient intake at 12 weeks in adults with obesity (BMI ≥ 30 kg/m2), classified into four energy-balance phenotypes (abnormal satiation, reduced postprandial satiety, low energy expenditure, emotional eating) (n = 77) who underwent PLI or SLI. Dietary intake was assessed by 24-h recalls and verified by a blinded registered dietitian. Results: Groups were compared at 12 weeks adjusting for baseline values. PLI was associated with lower total energy intake than SLI (1273 ± 182 vs. 1894 ± 176 kcal/day; p = 0.018), due to lower carbohydrate (464 ± 76 vs. 818 ± 73 kcal/day; p = 0.002) and fat intake (479 ± 76 vs. 697 ± 73 kcal/day; p = 0.036); absolute protein intake did not differ. However, protein comprised a greater proportion of energy intake in PLI (26.8 ± 1.6%) than SLI (19.8 ± 1.5%; p = 0.003), and dairy protein contributed more to total energy in PLI (6.8 ± 0.8% vs. 3.7 ± 0.7%; p = 0.004). Conclusions: PLI was associated with lower energy intake, mainly due to reduced carbohydrate and fat intake, and a higher relative contribution of protein, consistent with phenotype-based recommendations rather than macronutrient prescriptions. These findings suggest a potential role for personalized dietary approaches in obesity management. However, the non-randomized design does not allow causal inferences.