Much-craved combo of sugar and fat is why dieting feels impossible: study

By James Gamble via SWNS

A 'one-two punch' of simultaneous sugar and fat cravings is what makes dieting so difficult, new research has revealed.

Researchers analyzing the brain's reward systems discovered new brain-gut circuits for sugar and fat which make us crave unhealthy foods without even realizing it.

The team of American scientists found that the dangerous combination of these two cravings triggers a desire to overeat.

Until now, it has remained a puzzle to scientists why fats and sugars are particularly appealing to us.

But with this discovery comes hopes that these cravings can be combatted and finally make dieting far easier.

Although we understand food's powerful influences on our choices, the precise brain circuitry behind this has remained a mystery.

Scientists have uncovered that the vagus nerve sends internal sensory information from the gut to the brain about the nutritional value of food.

However, the molecular basis of the reward in the brain associated with what we eat has never been fully known.

This latest study, published in the journal Cell Metabolism, sought to unravel the internal neural wiring and revealed separate fat and sugar-craving pathways.

The study also revealed the concerning truth that a combination of these pathways overly triggers our desire to eat more than usual.

Dr. Guillaume de Lartigue, a lead author of the study from the Monell Chemical Senses Centre in the US said: "It's like a one-two punch to the brain's reward system.

"Even if the total calories consumed in sugar and fats stays the same, combining fats and sugars leads to significantly more dopamine release and, ultimately, overeating."

He added: "Food is nature's ultimate reinforcer but why fats and sugars are particularly appealing has been a puzzle.

"We've now identified nerve cells in the gut rather than taste cells in the mouth are a key driver.

"We found that distinct gut-brain pathways are recruited by fats and sugars, explaining why that donut can be so irresistible."

Dr. de Lartigue's team's research provides insights on what controls 'motivated' eating behavior, suggesting a subconscious internal desire to consume a diet high in both fats and sugar has the potential to do away with our efforts to keep weight off.

The researchers manipulated fat or sugar neurons in the vagus nerve systems of mice and demonstrated that both types of neurons cause a dopamine release in the reward centres of the brains of the mice.

They discovered two dedicated vagus nerve pathways: one for fats and another for sugars.

These circuits, originating in the gut, relay information about what we have eaten to the brain - setting the stage for cravings.

To determine how fats and sugars affect the brain, the team stimulated gut vagal nerves with light.

This induced the mice to actively seek stimuli - in this case, food - that engage these circuits.

The results indicated that sugar and fat are sensed by discrete neurons of the vagus nerve and engage parallel but distinct reward circuits to control nutrient-specific reinforcement.

The researchers also found that simultaneously activating both the fat and the sugar circuits creates a powerful craving synergy which prompted the mice to overeat.

The findings shed light on why dieting can feel like such a challenge: our brains may be subtly programmed to seek out high-fat, high-sugar combinations regardless of our efforts to resist.

Dr. de Lartigue added: "The communication between our gut and brain happens below the level of consciousness.

"We may be craving these types of food without even realizing it."

The team also hopes their research could be built on in the future to develop anti-obesity strategies and treatments, which would make dieting easier by altering gut-brain reward circuits to curb unhealthy eating habits.

"Understanding the wiring diagram of our innate motivation to consume fats and sugars is the first step towards rewiring it," Dr. de Lartigue said.

"This research unlocks exciting possibilities for personalized interventions that could help people make healthier choices, even when faced with tempting treats."