Weight cycling in women may harm cardiometabolic health and reduce brown fat activity

Brazilian researchers are warning about the impact of repeated cycles of intentional weight loss followed by unintentional weight gain on women’s cardiometabolic health. This “yo-yo effect” also reduces brown fat activity, which is necessary for burning energy. 

The researchers from the State University of Campinas (UNICAMP) studied 121 women aged 20–41 and divided them into two groups: those with no history of yo-yo dieting and “cyclers.” They found that the cyclers had more body and visceral fat and worse metabolic indicators.

Their finding suggests that the yo-yo effect negatively influences body composition, suggesting that obesity treatments should focus on sustainably reducing fat while preserving muscles and not just weight loss.

Understanding BAT

The study in Nutrition Research underscores the importance of brown adipose tissue (BAT), a type of fat that is increasingly gaining attention for its role in managing obesity, diabetes, and dyslipidemia (abnormal levels of lipids in blood).

BAT burns glucose and lipids to produce heat and release energy. On the other hand, white fat stores energy. BAT is also rich in mitochondria, which give cells energy and impart a brownish color and high metabolic activity, the researchers explain.

An infrared thermography camera captured the increase in temperature in the supraclavicular region, which indicates greater BAT activity (Image credit: Laura Ramos Gonçalves Gomes).Research on BAT has grown from believing it existed only in newborns a decade ago to its discovery in adults in 2009, especially around the neck, collarbone, and spine.

Focus on women

The researchers decided to study only women because laboratory databases show significant differences in the amount and activity of brown fat between men and women.

“The study focused on young women who were still outside the menopause period precisely to avoid hormonal interference that alters the distribution of body fat. Additionally, women tend to suffer from greater esthetic pressure and often resort to restrictive diets, which increases the occurrence of the yo-yo effect,” comments study author Ana Carolina Junqueira Vasques, professor at UNICAMP.

Those in the cycler group have three or more episodes of intentional weight loss over the past four years, followed by unplanned weight gain of at least 4.5 kg. Research has linked this pattern to restrictive dieting.

Assessing brown fat activity

In the study, participants were first placed in a heated room and then exposed to 18°C in another room to activate BAT. This helped researchers assess brown fat activity. 

“If the individual starts to shiver, they’ll expend additional energy. That’s why the temperature was maintained at 18°C, which is considered manageable cold,” Vasques explains.

She adds that BAT activity was monitored at various times in warm and cold rooms using an infrared thermography camera. “This camera takes images and captures exactly the hottest regions, painting them in a different color. Based on the intensity of this color, we can quantify how much BAT is activated in each participant.”

Participant body fat percentage, visceral fat, blood glucose, lipid profile, and blood pressure were also analyzed.

According to the results, the cyclists’ group had more body fat, worse metabolic indicators, accumulated more visceral fat, and reduced BAT.

“The yo-yo effect probably acts indirectly. Over successive cycles of weight loss and regain, there’s a progressive worsening of body composition, with recovery predominantly of fat and not muscle mass. Therefore, what really explains the lower brown fat activity isn’t the yo-yo effect alone but rather excess body fat,” says Vasques.

Since BAT activity can only be measured in research settings, not in routine examinations, she suggests obesity management does not just focus on weight loss.

“Obesity treatment strategies should prioritize body composition quality, long-term sustainable fat percentage reduction, and muscle mass preservation with multidisciplinary approaches and lasting behavioral changes.”

Although brown fat should be considered as part of weight loss, its importance lies in improving glucose and lipid metabolism, which helps protect against diabetes and cardiovascular risks, notes Vasques.

In a previous interview with Monteloeder by SuanNutra, we discussed its Metabolaid ingredient, which burns more energy, including fat sources, and stimulates the secretion of GLP-1.

In another discussion, AceBiome highlighted its strain, Lactobacillus gasseri BNR17, which was the first probiotic approved in South Korea for body fat reduction based on clinical trials demonstrating reduced visceral fat and improved gut health.