Diet & Thermogenesis: How Cutting Methionine & Cysteine Boosts Calorie Burn

The body’s response to cold – shivering, increased heart rate, and a surge in energy expenditure – is well known. But what if you could mimic those effects without stepping outside into freezing temperatures? Fresh research from the University of Southern Denmark suggests a dietary approach may hold the key, offering a potential pathway to weight loss by essentially “tricking” the body into burning more calories. The findings, published in the journal eLife, center around restricting intake of two specific amino acids: methionine and cysteine.

How Diet Can Mimic Cold Exposure

For years, scientists have understood that cold exposure reliably boosts energy expenditure in both mice and humans through a process called thermogenesis – the body’s heat production. This natural process burns energy, and researchers have been searching for ways to activate it without the discomfort of cold. Philip Ruppert and Jan-Wilhelm Kornfeld, obesity researchers at the Department of Biochemistry and Molecular Biology (BMB) at the University of Southern Denmark, took a different tack, investigating whether manipulating diet could achieve a similar result. Their work focused on the amino acids methionine and cysteine.

Through a series of experiments with mice, the team discovered that a diet low in these amino acids led to energy burning comparable to continuous exposure to 5°C (41°F). Mice on the restricted diet exhibited nearly the same level of energy expenditure and weight loss as those kept in the cold. This suggests that altering diet composition, rather than temperature, can be a powerful trigger for thermogenesis.

Methionine and Cysteine: What Role Do They Play?

Methionine and cysteine are sulfur-containing amino acids found in high concentrations in animal proteins – meat, eggs, and dairy products. They play crucial roles in various bodily functions, including protein synthesis and antioxidant defense. Though, the research indicates that high levels of these amino acids may, in some way, inhibit the body’s natural thermogenic processes. The study, likewise available as a preprint on bioRxiv, details how restricting these amino acids activated beige fat, a type of fat tissue located just under the skin.

“Fat was burned in beige fat during both cold induced thermogenesis and diet induced thermogenesis,” explains Ruppert, who is now at Cornell University. “This tells us that beige fat doesn’t care whether the burning is triggered by cold or by diet.” Beige fat is activated during cold exposure, and the researchers found it was also activated by the restricted diet, indicating a shared pathway for energy expenditure.

Beyond Weight Loss: Beige Fat and Metabolic Health

The activation of beige fat is significant because this type of fat is linked to improved metabolic health. Unlike white fat, which stores energy, beige fat burns energy. Increasing the activity of beige fat is a key target in obesity research, as it can help improve insulin sensitivity and reduce the risk of metabolic diseases. The study suggests that dietary manipulation could be a novel way to achieve this.

The mice in the study didn’t change their food intake or activity levels. they simply burned more energy due to the altered amino acid composition of their diet. “We saw a 20% increase in their thermogenesis,” says Kornfeld, a molecular biologist and professor with the Danish Diabetes and Endocrine Academy (DDEA). “They lost more weight, and it was not because they ate less or exercised more — they simply generated more heat.”

What Does This Mean for Humans?

Although the research is promising, it’s crucial to remember that it was conducted on mice. The effects of methionine and cysteine restriction in humans remain unknown. However, the researchers point out that vegetarians and vegans, who naturally consume lower levels of these amino acids due to their avoidance of animal products, may already be experiencing some of these benefits. As SciTechDaily reports, the study raises the possibility that similar effects could be observed in humans.

“We haven’t tested a methionine/cysteine-restricted diet in humans, only in mice, so we can’t say for certain that the same effect would occur in people — but it’s absolutely a possibility,” Ruppert notes. It’s important to emphasize that this is not a recommendation to drastically alter one’s diet without consulting a healthcare professional. Amino acids are essential nutrients, and restricting them could have unintended consequences.

Future Research and Potential Therapies

The researchers are now exploring whether these findings could lead to new obesity treatments. They are interested in developing functional foods naturally low in methionine and cysteine, and investigating whether patients undergoing weight loss treatments like Wegovy might experience additional benefits from a diet restricted in these amino acids. The study also opens up avenues for further research into the mechanisms by which methionine and cysteine influence thermogenesis and beige fat activation.

The next steps involve understanding the precise molecular pathways involved and conducting human trials to determine the safety and efficacy of this dietary approach. It’s a long road from mouse studies to clinical applications, but the initial findings offer a compelling new perspective on the potential of diet to influence energy expenditure and metabolic health. Further investigation will be needed to determine if this dietary strategy can be safely and effectively translated to humans, offering a novel approach to weight management and metabolic disease prevention.