The effects of exercise on the neuronal response to food cues

Abstract

Increased physical activity is associated with successful long-term weight loss maintenance due to mechanisms likely more complex than simply increased energy expenditure. The impact of physical activity on the central regulation of food intake may be an important mechanism of this effect. The objective of this study was to examine the effects of exercise training and acute exercise on the neuronal response to food cues as well as eating behaviors. fMRI was performed in the fasted state at baseline and again after a 6 month progressive exercise intervention (supervised, 5 days/wk) both with and without an acute exercise bout in 12 overweight/obese (5 women, 7 men; BMI 33 ± 4 kg/m(2)) healthy adults. fMRI data were acquired while subjects were presented with visual stimuli of foods of high hedonic value as compared to neutral control objects. Questionnaires on eating behaviors, ratings of appeal and desire for foods, and ratings of appetite (hunger, satiety, prospective intake) using visual analog scales were also performed at baseline and again after the 6-month exercise intervention. While only a trend was observed for a reduction in body weight (102 ± 5 to 99 ± 6 kg, p=0.09), a significant reduction in fat mass was observed (36.4 ± 2.8 to 33.7 ± 3.2 kg, p=0.04), although as expected changes in fat mass were variable (-10.0 to +3.7 kg). Chronic exercise was associated with a reduction in the neuronal response to food, primarily in the posterior attention network and insula. A significant positive correlation between the change in fat/body mass and the change in insula response to food cues with chronic exercise was observed. An acute exercise bout attenuated the effects of chronic exercise. The exercise intervention, however, did not impact any of the measures of appetitive behavior. In summary, despite no effects on behavioral measures of appetite, chronic exercise training was associated with attenuation in the response to visual food cues in brain regions known to be important in food intake regulation. The insula, in particular, appears to play an important role in the potential exercise-induced weight loss and weight loss maintenance.

Figure 1

Changes in fat mass in response to a 6-month exercise intervention.

Figure 2

The neuronal response across all subjects to images of foods of high hedonic value as compared to nonfood objects at baseline before the exercise intervention. Greater activation is observed in a network of brain regions, including the bilateral insular cortices, somatosensory cortices, parietal cortices and visual cortex. Data are shown in the radiological convention (right hemisphere on the left).

Figure 3

The difference in neuronal response to foods of high hedonic value as compared to nonfood objects following “chronic exercise” as compared to “baseline”. Reduced responses to visual food cues following “chronic exercise” were observed in the bilateral parietal cortices, left insula and visual cortex. No differences between “baseline” and “chronic + acute exercise” were observed. Inset: insula responses in the “chronic + acute exercise” were intermediate between “baseline” and “chronic exercise” conditions.

Figure 4

Correlation between neuronal response following exercise and the change in fat mass (a) and body weight (b). The difference in anterior insula responses between the baseline condition and “chronic exercise” were positively correlated with change in fat mass and body weight.