The Effect of a Mediterranean Diet With or Without Calorie Restriction on Cognition, Lifestyle, and Metabolic Health of Obese, Predominately Non-Hispanic Black Older Adults

OBJECTIVES: To compare the effect of a Mediterranean Diet with (Med-WL) or without caloric restriction (Med-A) for intentional weight loss (IWL) versus a typical diet control (TDC) on cognition, lifestyle and cardiometabolic health. METHODS: A randomized clinical trial of obese, predominately non-Hispanic black, older adults was conducted between June 2017 and December 2020 at community sites in Chicago, Illinois. Participants (n = 185) were randomized (2:2:1) to 1 of 3 groups for 8-months: Med-WL, Med-A, or TDC. The primary outcome was change from baseline to post-intervention in three cognitive composite scores: attention, information & processing; executive function; and learning, memory & recognition. Secondary outcomes included changes in MedDiet adherence, physical activity, body weight, total and regional body fat, blood pressure, fasting blood lipids, glucose, insulin and C-reactive protein (CRP). RESULTS: Participants were 85.9% female with a mean (SD) age of 66.3 (6.1) years, and retention was similar across arms (85.3% Med-WL, 87.7% Med-A, 94.6% TDC, p = 0.36). The MedDiet interventions did not affect cognitive composite scores. MedDiet adherence improved significantly more in Med-WL (adjusted mean [95% CI] score change, +6.3 [4.9 to 7.6] points) and Med-A (+4.8 [3.4 to 6.2] points) relative to TDC (+0.6 [−1.3 to 2.4] points, p < 0.05). Weight loss was significantly greater in Med-WL (adjusted mean [95% CI]: −4.6 [(-5.6 to −3.5] kg) than in Med-A (-2.6 [−3.7 to −1.5] kg, p < 0.05) and TDC (−0.6 [−2.1 to 0.8] kg, p < 0.05). Reduction in central body fat was significantly greater in the MedDiet arms (adjusted mean change [95% CI], Med-WL: −147 [−235 to −59] gm; Med-A: −162 [−248 to −76] gm) than in TDC (+91 [−18 to 200] gm, p < 0.05). For cardiometabolic health, only fasting insulin changed significantly in Med-WL (adjusted mean change [95% CI]: −2.2 [−3.2 to −1.2] uIU/mL) relative to Med-A (−0.6 [−1.6 to 0.4] uIU/mL, p < 0.05) and TDC (−0.5 [−1.8 to 0.8] uIU/mL, p < 0.05). CONCLUSIONS: An 8-month MedDiet lifestyle intervention with or without caloric restriction for IWL did not produce superior effects on cognitive function compared to a TDC, but it did produce significant effects on diet quality, total body weight and central body fat. FUNDING SOURCES: National Heart, Lung And Blood Institute; National Cancer Institute; National Institute On Minority Health And Health Disparities.