“Restriction of Dietary Fat, but Not Carbohydrate, Alters Brain Reward Circuitry in Adults With Obesity”, Valerie L. Darcey, Juen Guo, Amber Courville, Isabelle Gallagher, Jason A. Avery, W. Kyle Simmons, John E. Ingeholm, Peter Herscovitch, Alex Martin, Kevin D. Hall2022-04-20 (exercise, neuroscience)⁠:

Weight 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 an 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.