Alternating between a standard calorie-restricted diet plan and one high in fat and sugar, which can result in regaining lost weight and then some, is not just down to psychology and behavior. This kind of weight-loss sabotage – or yo-yo dieting – has a surprising biological driver: The gut.
Researchers from the Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), the French research Institute for agriculture, food and the environment, have discovered a key mechanism that drives poor diet choices following calorie-restricted periods of eating. These findings link gut microbiota alterations directly to reward-driven overeating, which could underpin the failure of dietary interventions in maintaining weight loss.
The scientists set out to investigate how repeated cycles of calorie restriction and refeeding – yo-yo dieting – affected the regulation of food intake, especially in regards to "hedonic" (pleasure-driven) appetite, and to determine the role of the gut microbiota in this process. They tested the hypothesis that the gut-brain axis could be more involved in this restricted-hedonic eating than we've appreciated.
Researchers put mice on an alternating food intake – one week of a Western diet and two weeks on a chow diet. The Western diet was representative of a high-fat, high-sugar eating pattern, while the chow diet featured low-fat and unprocessed foods.
What they found was that within eight hours of finishing the two weeks on the chow diet, the mice had a significant energy intake, which resembled binge-eating behaviors. And this hedonic feeding also occurred when the mice would normally be resting or not taking on extra energy. In other words, the mice were displaying disordered eating behaviors.
Fecal analysis found that the "low calorie-high calorie"-cycling mice had distinct changes in their microbiota, with a notable drop in species richness, compared to non-yo-yo-dieting animals. Interestingly, when their microbiota samples were then transferred into the guts of healthy mice, these animals also developed the same compulsive eating behaviors. They didn't just eat more at unusual times, but were driven to choose high-fat and high-sugar foods – something they'd never done before.
What's more, the researchers also observed that the brains of these mice had changed, with reward genes newly excited in the striatum. Changes were seen in the brain stem, which is integral to communication along the gut-brain axis.
And these mice gained more weight in five days than a group of rodents who had not cycled between diets nor had a microbiota transfer from the yo-yo dieting animals.
While not tested on humans, the findings nonetheless demonstrate that there appears to be more to yo-yo dieting behavior and why restriction often leads to excess – and weight gain – than willpower. That said, the researchers noted that the study has its limitations; by isolating the gut's role, other likely influences on bingeing behavior – food taste, more complex components of reward signaling in the brain – were not factored in. And the mice who'd come off the low-fat diet to gorge on high-sugar and high-fat foods were, unlike humans, probably not thinking about potential weight gain.
But this discovery makes a case for a human study, as it opens the door to new treatments that better serve people trying to lose weight who might be stuck in this yo-yo dieting cycle. As anyone who has tried to lose weight and failed, and tried again, knows, it's incredibly complex and also personal – but by addressing the gut's change, it could bolster one's chances of succeeding with long-term weight loss and maintenance.
"In this study we showed that alternation between high-energy and standard diet durably remodels the gut microbiota toward a profile that is associated with an increase in hedonic appetite and weight gain," the researchers noted. "Using gut microbiota transfer, we established that this yo-yo microbiota signature affects hedonic appetite. More work is definitely needed to fully understand the mechanisms at play in this model, especially regarding the gut microbiota to brain transduction pathways involved in this weight cycling-induced altered eating behavior."
The study was published in the journal Advanced Science.
Source: Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement
