Visceral fat—also called abdominal or belly fat—is necessary to help cushion your organs. But when there’s too much of it, it can increase your risk for metabolic syndrome, a condition that increases your risk of heart disease, diabetes and stroke. 

Metabolic syndrome is a cluster of other conditions, including larger waist circumference, high blood pressure, high triglycerides, high blood sugars and low HDL (beneficial) cholesterol. Metabolic syndrome is defined as having three or more of these conditions. 

While metabolic syndrome used to be primarily found in the older population, rates have steadily climbed in younger people. There is evidence that 1 in 5 young adults in the U.S. now has metabolic syndrome.

The good news is that there are many things you can do to lower your risk. For example, we previously reported on Vanderbilt University Medical Center research that suggested swapping high-carbohydrate snacks with nuts helped reduce abdominal fat. These same researchers wanted to dig deeper and look at the “why” behind these results. They published their findings in May 2025 in Clinical Nutrition. Let’s break down what they found.

How Was This Study Conducted?

Researchers recruited 84 adults, aged 22 to 36, with one or more metabolic syndrome risk factors. Those factors include:

• Waist circumference ≥89 cm for men and ≥80 cm for women
• HDL cholesterol ≤40 mg/dL for men or ≤50 mg/dL for women
• Fasting blood glucose levels ≥100 mg/dL
• Blood pressure >130/85 mm Hg
• Blood triglycerides ≥128 mg/dL

Before the trial officially began, there was a two-week run-in period. That was done so that all participants could start on the same playing field regarding diet. Participants received nutrition counseling and recommendations based on the 2020-2025 Dietary Guidelines for Americans, as well as a daily supply of high-carbohydrate snacks. They were also instructed to avoid all types of nuts and nut butters during this time.

Following the run-in period, participants were randomly divided into two groups, which were evenly distributed based on BMI so that each group contained about an equal number of those in the “normal” BMI and “overweight” BMI categories. One group was assigned tree nuts as snacks; the other group was assigned high-carb snacks. 

The nut group was provided with two snacks each day, with each one including 33.5 grams of raw, unsalted tree nuts. The mixed nuts included almonds, walnuts, pecans, macadamia nuts, hazelnuts, pistachios and cashews. They ate slightly more than ¼ cup per snack, or about ½ cup of tree nuts per day. The high-carb snack group was provided with unsalted pretzels, animal crackers, graham crackers and some granola bars. 

After the two-week run-in period and at the end of the study, participants had fasting bloodwork done, as well as abdominal subcutaneous (under the skin) adipose (fat) tissue aspirated with a small needle. Researchers analyzed the fat tissue for differences in gene expressions and fatty acid composition. 

Why did they aspirate abdominal adipose tissue? Adipose tissue stores different types of fatty acids, which can be released into your bloodstream when your body is in need of an energy source. The types of fatty acids can change over time, depending on what you eat. Your genes within the fat tissue influence how the fat functions. These are those “whys” we mentioned earlier. The researchers wanted to understand why their first study showed a reduction in waist circumference in the nut group. 

What Did This Study Show?

After statistical analyses were run, the results suggested that the nut group increased their total fat intake and had significant improvements in their saturated fat-to-unsaturated fat ratio. In particular, they saw increases in monounsaturated and polyunsaturated fat intake, while having no change in their saturated fat intake. 

Regarding the types of fatty acids stored in the abdominal adipose tissue, the nut group saw changes but they were not yet clinically significant. However, there were increases in oleic acid, a type of monounsaturated fat, trending toward a more favorable ratio of unsaturated to saturated fats. Researchers note that the length of the study period—16 weeks—was most likely not long enough to see a remarkable change in stored fatty acids, but that this may have changed with a longer follow-up period.

While there were no significant changes in the types of fats stored, there were noteworthy changes in the adipose tissue gene expression in the nut group—but not the high-carb snack group. Specifically, the various genes that showed increased expression in the nut group were those connected to

• breaking down fat cells
• assisting HDL cholesterol in removing “bad” cholesterol
• supporting the immune system and reducing inflammation. 

All of these factors help reduce metabolic syndrome and chronic disease risk. 

This study had several limitations. First, the small sample size reduces statistical power, since having more participants is almost always better where studies are concerned. Sixteen weeks may not have been long enough to see changes in abdominal fat. Lastly, self-reporting food diaries lend themselves to bias and inaccurate recollection.

How Does This Apply to Real Life?

Nuts are loaded with brain- and heart-healthy fats, plant protein, antioxidants, vitamins and minerals. Eating them regularly has been linked to a healthier heart, brain, blood sugar levels and weight.

The key with choosing your nuts—besides picking ones you like—is to choose unsalted raw or dry-roasted nuts most of the time, as oil-roasting can add unnecessary fat to your nuts. If you prefer some salt, choose lightly salted. Even better, mix unsalted with lightly salted to get your taste buds used to less salt, since eating too much sodium is connected to increased blood pressure—which is the opposite of what you’re trying to accomplish by noshing on nuts. 

It’s important to remember that no one food or food category is a magic pill for weight loss or disease risk reduction. It takes a healthy-habit team effort. For example, eating more plants in general, which includes nuts, may help reduce abdominal fat. We’ve got meal plans specifically designed to help reduce abdominal fat, including 30-day and seven-day plans.

Fat isn’t the only thing that can increase waist circumference. That bloating in your hands, face, feet and middle? It could be a result of eating too much salt.

Gas and bloating can also result from eating what is typically considered “healthy” foods, like broccoli, cauliflower and beans. Figure out which foods or sneaky additions to foods, like inulin and sugar alcohols—including those in gum—are causing the bloat and remove them for a while before slowly adding them back in to see how your body reacts. When in question, meet with a registered dietitian to help you figure it out.

Regular physical activity can also help reduce abdominal fat, as can getting plenty of quality sleep and taking time throughout the day to rest. Of course, a lack of sleep results in higher stress levels—and so the cycle goes. 

The Bottom Line

This study suggests that swapping high-carb snacks with nuts may help stimulate genes stored in abdominal fat that influence factors related to metabolic syndrome, including how fat is used, levels of inflammation, cholesterol and immunity. Choose your favorite unsalted raw or dry-roasted nuts and use them as snacks or incorporate them into your meals. Toss some into your oatmeal or yogurt, use them in place of croutons on your salad or pair nut butter with dark chocolate for a tasty, heart-healthy ending to a meal.