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Study reveals surprising outcomes of long-term dieting

[Mar. 27, 2023: JD Shavit, The Brighter Side of News]

Researchers have developed a small-molecule drug that prevents weight gain and adverse liver changes. (CREDIT: Getty Images)

Many people who have dieted are familiar with the yo-yo effect: after the diet, the kilos are quickly put back on. But what causes this phenomenon? Researchers from the Max Planck Institute for Metabolism Research and Harvard Medical School have now shown in mice that communication in the brain changes during a diet.

The nerve cells that mediate the feeling of hunger receive stronger signals, so that the mice eat significantly more after the diet and gain weight more quickly. In the long term, these findings could help develop drugs to prevent this amplification and help maintain a reduced body weight after dieting.


"People have looked mainly at the short-term effects after dieting. We wanted to see what changes in the brain in the long term," explains Henning Fenselau, a researcher at the Max Planck Institute for Metabolism Research, who led the study.

The study, which was published in the scientific journal Nature Communications, investigated the impact of dieting on neural circuits in the hypothalamus, the part of the brain that controls hunger and other vital bodily functions. The researchers used a group of mice and put them on a diet to assess which circuits in the brain changed. They particularly examined a group of neurons in the hypothalamus, the AgRP neurons, which are known to control the feeling of hunger.


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Co-author Bradford Lowell from Harvard Medical School adds: "This work increases understanding of how neural wiring diagrams control hunger. We had previously uncovered a key set of upstream neurons that physically synapse onto and excite AgRP hunger neurons. In our present study, we find that the physical neurotransmitter connection between these two neurons, in a process called synaptic plasticity, greatly increases with dieting and weight loss, and this leads to long-lasting excessive hunger.”

The researchers say that their findings could have important implications for the development of new treatments for obesity and related conditions. "Our results suggest that changes in the brain are a critical factor in the long-term regulation of body weight and that targeting these changes could be an effective way to prevent weight regain after dieting," says Fenselau.


Experts in the field have praised the study for its rigor and innovative approach. "This study provides important new insights into the complex mechanisms underlying the regulation of appetite and weight," says Professor John Blundell, a leading expert in the field from the University of Leeds. "It suggests that the brain plays a key role in maintaining body weight over the long term, and that targeting neural circuits could be an effective way to prevent weight gain after dieting."

Graphical Abstract: Weight loss upon caloric deprivation activates PVH neurons that co-express PACAP. (CREDIT: Cell Metabolism)

Blundell adds that the findings could have important implications for the development of new treatments for obesity and related conditions. "This study is a great example of how basic research can lead to new therapies for complex health problems," he says.


Other recent studies on the long-term effects of dieting

A recent study published in the Journal of Nutrition and Metabolism analyzed the long-term effects of low-carb diets on weight loss and other health markers. The study followed participants for up to 10 years after they had completed a low-carb diet. The results showed that those who maintained a low-carb diet were able to maintain their weight loss and improve their blood lipid profile over the long term. However, the study also found that participants who had gone back to a higher carb diet had regained some of their weight.

The researchers noted that while low-carb diets can be effective for weight loss, they may not be suitable for everyone. They also emphasized the importance of long-term maintenance of healthy eating habits to avoid weight regain.

Another recent study published in JAMA Internal Medicine examined the long-term effects of calorie restriction on weight loss and lifespan. The study followed participants who had restricted their calorie intake by 25% for two years, and then tracked their progress for another six years.

The results showed that while participants had lost weight during the two-year calorie restriction period, they had regained some of it during the six-year follow-up period. However, the study also found that calorie restriction had led to improved biomarkers of aging, such as lower levels of oxidative stress and inflammation.


The researchers noted that calorie restriction may not be sustainable for everyone, and that the long-term effects of the diet on health outcomes are still unclear. They also emphasized the importance of combining calorie restriction with healthy eating habits to maintain long-term health benefits.

Consensus so far

Overall, these studies highlight the importance of considering the long-term effects of dieting on weight loss and overall health.

The studies show that different types of diets may work better for different individuals, and that finding an approach that works for you and is sustainable over the long term is crucial.

The traditional approach of focusing solely on calorie restriction may not be the most effective strategy for long-term weight loss and health. Instead, it may be more beneficial to focus on the quality of the foods we eat, such as consuming more whole foods and reducing highly processed foods.

The studies highlight the importance of ongoing support and accountability to maintain weight loss over time. Strategies such as regular check-ins with a healthcare professional or joining a support group can help individuals stay on track with their healthy habits.


Finally, the studies underscore the need for more research on the long-term effects of different diets on weight loss and health outcomes. While there is some evidence to suggest that certain diets may be more effective for long-term weight loss, more research is needed to determine the optimal approach for different individuals and to better understand the underlying mechanisms of weight loss and weight regain.



For more science and technology stories check out our New Discoveries section at The Brighter Side of News.


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