Plain language summary
Weight loss diets that use total meal replacement shakes have been shown to reduce food cravings compared to typical reduced-calorie diets. The mechanism for this is unclear. This study examined the effects of a 3-week 1120 kcal per day meal replacement diet compared to a reduced calorie diet on activity in areas of the brain associated with food cravings. Thirty-two obese adults participated in the study. Before and after the study, the participants were given magnetic resonance imaging (MRI) scans to measure activity in different areas of the brain. They were also questioned on food cravings and weighed. The group following the meal replacement diet experienced a significant weight loss of 4.87 kg, a reduction in body fat of 2.19 kg and reduced their overall food cravings. The reduced calorie diet group also experienced significant weight loss and a reduction in body fat (2.37kg and 1.64kg, respectively) but less than the meal replacement group. The meal replacement group experienced reduced cravings compared to the reduced calorie diet group. MRI scans suggested that this was due to changes in activity in the food reward related regions in several areas of the brain, resulting in an increase in executive control. The authors concluded that meal replacement diets may increase executive control within the brain, leading to a reduction in food cravings and weight loss.
Abstract
OBJECTIVES Calorie restriction via total meal replacement (TMR) results in greater reduction of food cravings compared to reduced-calorie typical diet (TD). Direct evidence of the impact of these interventions on human brain fMRI food-cue reactivity (fMRI-FCR) and functional connectivity is absent. We examined the effects of a 3-week 1120 kcal/d TMR intervention as compared to an iso-caloric TD intervention using an fMRI-FCR paradigm. METHODS Thirty-two male and female subjects with obesity (19-60 years; 30-39.9 kg/m2) participated in a randomized two-group repeated measures dietary intervention study consisting of 1120 kcal/d from either 1) TMR (shakes), 2) TD (portion control). Pre-intervention and following the 3-week diet fMRI-FCR, functional connectivity, food cravings (Food Craving Inventory) and weight were considered. RESULTS Compared to TD, TMR showed increased fMRI-FCR of the bilateral dorsolateral prefrontal (dlPFC), orbitofrontal, anterior cingulate, primary motor and left insular cortices and bilateral nucleus accumbens regions in the post-intervention state relative to the pre-intervention state. Compared to TD, TMR was also associated with negative modulation of fMRI-FCR of the nucleus accumbens, orbitofrontal cortex and amygdala by dlPFC. Reduced body weight (4.87 kg, P < 0.001), body fat (2.19 kg, P = 0.004) and overall food cravings (0.41, P = 0.047) were seen in the TMR group. In the TD group reduced body weight (2.37 kg, P = 0.004) and body fat (1.64 kg, P = 0.002) were noted. Weight loss was significantly greater in TMR versus TD (2.50 kg, P = 0.007). CONCLUSIONS Greater weight loss and reduced cravings, coupled with stronger activations and potential negative modulation of the food reward related regions by the dlPFC during exposure to visual food cues is consistent with increased executive control in TMR vs. TD.
Methodological quality
Allocation concealment
:
No
