While alcohol is widely recognized as a source of empty calories providing approximately seven kilocalories per gram without essential nutrients, recent findings suggest it also actively alters eating behavior. A study published in Obesity Reviews by researchers from the Charles Perkins Centre at the University of Sydney reveals that alcohol consumption in an obesogenic environment drives individuals toward ultra-processed foods. The mechanism involves the elevation of fibroblast growth factor 21 (FGF-21), a hormone secreted by the liver, which promotes the craving for protein and foods with umami flavor profiles.
The study analyzed data from over 9,000 participants and found that for every standard drink consumed, intake of proteins and salty foods increased by approximately seven grams, while consumption of sweet foods decreased. However, weight gain was primarily observed in participants who paired alcohol with what researchers term "protein lures." These are salty, ultra-processed snacks that lack actual protein content. To satisfy the biological signal for protein triggered by the hormone, individuals consume excessive amounts of these energy-dense foods, resulting in a net caloric surplus and increased weight.
Amanda Grech, the study's lead author, explained that alcohol induces weight gain not merely through its own caloric content but by pushing people to eat tasty, ultra-processed items or protein-diluted foods like fatty processed meats. Although this specific study did not measure FGF-21 levels in participants, previous research supports the link. A 2018 study in Molecular Metabolism involving Oktoberfest attendees demonstrated that excessive alcohol consumption drastically raises blood levels of FGF-21.
Diego Bellido, president of the Spanish Society of Obesity (SEEDO), noted that while the direct hormonal measurement was absent, the mechanistic hypothesis is plausible and consistent with population data. He emphasized that this work shifts the understanding of the relationship between alcohol and obesity, highlighting how metabolic signals like FGF-21 can modify dietary behavior beyond simple calorie addition.
Experts further clarified the role of protein quality in satiety. Ana Belén Crujeiras from the Santiago Health Research Institute explained that high-quality proteins quickly trigger satiety signals in the brain. Conversely, ultra-processed salty foods provide umami flavor without sufficient protein, making it difficult to reach satiety and leading to overeating. Previous studies, including one published in Cell Metabolism in 2016, identified FGF-21 as a specific endocrine sensor for protein scarcity, with levels rising under low-protein, high-carbohydrate diets.
Crujeiras highlighted that in her own research comparing ketogenic diets to bariatric surgery, patients undergoing surgery showed elevated FGF-21 levels during the acute phase due to protein deficiency and inflammation, whereas those on adequate protein diets saw levels drop. This supports the theory that alcohol induces a perceived protein deficit, triggering FGF-21 secretion and subsequent cravings. To counteract this effect, experts recommend reducing alcohol intake or pairing it with high-protein, less processed foods while avoiding environments filled with salty snacks and energy-dense appetizers.
Sources: El País Ciencia.