Obesity is associated with an accelerated cognitive decline. Aerobic fitness has a protective effect on cognition in older adults, but no study has investigated this effect in obese individuals. The present study aimed to 1) compare cognitive function in lower-fit (LoFit) and higher-fit (HiFit) obese individuals compared with nonobese individuals, and 2) examine the association between exercise variables (including hemodynamic variables) and cognitive function in obese individuals.
Fifty-four obese and 16 nonobese individuals performed a maximal cardiopulmonary exercise test (with gas exchange analysis and noninvasive hemodynamic measurement) and cognitive tests assessing short-term and working memory, processing speed, executive function, and long-term verbal memory. Obese individuals were divided into 2 groups according to their median aerobic fitness divided by lean body mass to form a group of LoFit obese (n = 27) and a group of HiFit obese (n = 27) individuals.
A total of 14 nonobese individuals and 49 obese individuals were included in the final analysis (HiFit: n = 26, LoFit: n = 23). Compared with LoFit obese, HiFit obese participants had greater performances in executive function (P = 0.002) and short-term memory (P = 0.02). Nonobese and HiFit obese participants showed equivalent performances in all domains of cognition. In obese individuals, aerobic fitness was the only independent predictor for short-term memory (R ² = 0.24; P < 0.001), working memory (R ² = 0.16; P = 0.02), processing speed (R ² = 0.22; P = 0.01), and executive function (R ² = 0.49; P = 0.003), but not for long-term verbal memory (R ² = 0.15; P = 0.26).
HiFit obese individuals showed greater short-term memory and executive function performances compared with LoFit obese individuals, suggesting that aerobic fitness could help preserve cognitive function despite the presence of obesity.