What the researchers call the "fructose survival hypothesis" brings together most of the dietary hypotheses of obesity, including the two that have been most incompatible with each other—the energy balance theory, which proposes that too much food (and primarily fat) drives obesity, and the carbohydrate-insulin model, which puts carbohydrates at the center of weight gain.

Essentially, the energy balance theory and the carbohydrate-insulin theory, which put a litany of metabolic and dietary drivers at the center of the obesity epidemic, are all pieces of a puzzle unified by one last piece: fructose. Fructose is what triggers our metabolism to go into low power mode and lose our control of appetite, but fatty foods become the major source of calories that drive weight gain.

To unify these theories in particular, the researchers say we can look to hibernating animals as an example. When we're hungry and low on active energy, we go into survival mode. Animals know to forage for food when energy levels begin to fall; it’s why bears eat fruit to prepare for winter. Fruits are high-fructose foods, and fructose significantly stifles active energy. Fat acts as stored energy, but eating high-fructose foods blocks the replacement of active energy from fat storage, keeping active energy low like a bear preparing for a long winter's nap.

The fructose survival hypothesis views obesity as a low-energy state. Identifying fructose as the conduit that redirects active energy replacement to fat storage shows that fructose is what drives energy imbalance, which unites theories.

While more work is needed to fully validate this unifying hypothesis, this is a hopeful first step in potentially identifying more targeted preventions for obesity and related metabolic imbalance management.