Restriction of dietary fat, but not carbohydrate, affects brain reward regions in adults with obesity

Abstract

SUMMARYWeight loss diets often restrict either fat or carbohydrate, macronutrients that are sensed via distinct gut-brain pathways and differentially affect peripheral hormones and metabolism. To investigate whether reductions in dietary fat versus carbohydrate alter brain reward circuitry, we measured dopamine D2/3 receptor binding potential (D2BP) using PET and neural activity in response to visual food cues using fMRI in 17 inpatient adults with obesity during a eucaloric baseline diet and on the fifth day of isocaloric diets selectively reduced in either dietary fat or carbohydrate, in random order. Reduction of dietary fat, but not carbohydrate, decreased D2BP and decreased neural activity to food cues in brain reward regions. After the reduced fat diet, ad libitum intake shifted towards foods high in both fat and carbohydrates. These results suggest that dietary fat restriction increases tonic dopamine in brain reward regions thereby affecting food choice in ways that may hamper diet adherence.IN BRIEFDarcey et al. found that selective reduction of dietary fat, but not carbohydrate, resulted in changes in brain dopamine receptor binding potential and neural activity in response to food cues, consistent with increased tonic dopamine and resulting in greater subsequent consumption of rewarding foods high in both fat and carbohydrate.HIGHLIGHTSCompared to a eucaloric baseline diet, selective reduction of dietary fat, but not carbohydrate, significantly decreased both dopamine D2/3 receptor binding potential and neural activity to visual food cues in brain reward regions.Multimodal neuroimaging suggests that reduction of dietary fat, but not carbohydrate, increased tonic brain dopamine and influenced food choices in ways that may hamper diet adherence.

Alterations in type 2 dopamine receptors across neuropsychiatric conditions: A large-scale PET cohort

“…Several recent studies have addressed the conflicting findings regarding the link between overweight and D 2 R (Dagher, 2012;Darcey et al, 2023;Horstmann et al, 2015). They suggest that BMI and striatal D 2 R availability may not be strictly linear.…”