Overall, it’s no surprise that we eat too much sugar. Now, scientists have discovered that when our craving for sweets is satisfied, the craving subsides and is replaced by sudden cravings for greasy foods, which can wreak havoc on metabolic function and weight.
Researchers at Sweden's Umeå University have discovered a hormonal mechanism triggered by excessive sugar intake that leads to cravings for fatty foods. In a study of fruit flies (Drosophila melanogaster), sugar intake quickly signals the endocrine system to eat some fat to avoid what it perceives as malnutrition.
Co-author Mattias Alenius, professor in the Department of Molecular Biology, explained: "Consuming too much sugar will reduce the craving for sweets but increase fat intake, and vice versa. This ensures that the flies get enough sugar and fat as nutrients."
In 2022, the research team found that even a slight increase in sugar intake induced the secretion of the hedgehog (Hh) hormone. Although circulating Hh helps suppress sweet taste perception and preference, it greatly enhances fatty acid receptors.
In this study, the scientists found that excess fat induces adipose tissue to secrete Upd2, the human equivalent of leptin, into the fly's "blood" - hemolymph. This results in a suppression of the taste for fat, replaced by an increased desire for sugary foods.
This reciprocal regulation suggests that excessive consumption of sugar or fat can signal to needed hormones that the other is deficient and in need of balance.
"It's a tug-of-war between sugar and fat, rather than limiting total calories as we would like," Arrhenius said. "Presumably humans have similar compensatory mechanisms as flies, which means we prefer to eat as much fat as sugar. Generally speaking, an American cheesecake is the best way to drive our desire to eat."
The researchers plan to adapt the study to human subjects, hoping to get similar responses to the hormonal triggers in flies.
"We humans perceive fat as a taste, and it remains to be seen whether these findings apply to us as well. It deserves further study."
The research was published in the journal Cell Reports.