Could unfiltered coffee help reduce visceral fat, aid weight loss?

• Cafestol is a natural compound found in unfiltered coffee that may benefit certain aspects of metabolic health.
• New research suggests that 6 milligrams of cafestol twice daily for 12 weeks might slightly reduce weight and body fat but not improve insulin sensitivity or glucose tolerance.
• Experts say more research is needed, but in moderation, consuming unfiltered coffee may offer health benefits.

Cafestol is a natural diterpene compound found in coffee, particularly coffee brewed through unfiltered methods, such as boiled, Turkish, French press, and espresso coffee.

It adds to coffee’s flavor and aroma and may possess certain health benefits.

In recent years, a team of Danish researchers has studied cafestol’s influence on insulin sensitivity and other metabolic health markers. Their initial findings suggested that cafestol might help prevent type 2 diabetes.

In cell studies, they observed that cafestol increases insulin secretion and enhances glucose uptake, while in mouse models of diabetes, it improved insulin sensitivity and reduced blood glucose (sugar) levels.

They also explored the effects of cafestol — and kahweol — in participants with abdominal obesity and type 2 diabetes.

They found that these compounds appeared to briefly lower glucose, particularly in those with impaired glucose tolerance or fasting glucose or with type 2 diabetes.

In their latest randomized controlled trial — published in the journal Nutrients — the researchers aimed to assess whether pure cafestol affects insulin sensitivity and glucose tolerance in healthy individuals with high waist circumference, which is a diabetes risk factor.

Their novel findings suggest that 6 milligrams (mg) of cafestol twice daily for 12 weeks may lead to slight weight and body fat loss, but not significantly improve insulin sensitivity or glucose tolerance.

The study’s limitations prevent conclusive results, but it offers valuable insights for future research on cafestol’s potential role in helping prevent type 2 diabetes.

The present double-blinded randomized control trial investigated the impact of a 12-week cafestol supplementation on:

The study took place at the Steno Diabetes Center Aarhus, Aarhus University Hospital in Denmark.

• greater than 102 centimeters (cm), or 40 inches for men
• greater than 88 cm, or 35 inches for women.

Eligible participants were not pregnant or breastfeeding, did not have type 2 diabetes, hemoglobin A1C (HbA1c) readings above 6.5%, or other significant conditions, and were not taking medications for the treatment of diabetes.

Researchers randomized participants to receive 6 mg capsules of cafestol or a placebo twice daily at breakfast and dinner over a period of 12 weeks.

Participants could drink unlimited amounts of paper-filtered drip coffee and instant coffee, which contain negligible cafestol. However, they were limited to just one unfiltered coffee beverage — such as French press, boiled coffee, or espresso — per day for the duration of the study.

Initially and at various points during the study, they visited the study center and were fitted with continuous glucose monitors (CGMs) to monitor blood glucose, and a 24-hour ambulatory blood pressure monitor to blood pressure.

As the study progressed, they provided fasted blood samples and underwent mixed-meal testing, MRI scans of body fat, and insulin tests, followed by the 12-week intervention.

Six weeks after the intervention, the researchers assessed participants’ liver and kidney function through blood samples.

Researchers thought that taking cafestol for 12 weeks might improve insulin sensitivity and other metabolic markers.

Contrary to expectations, they found that taking 6 mg of cafestol twice a day did not improve glucose tolerance or insulin sensitivity.

However, compared to the placebo, cafestol did reduce body weight, visceral fat, and a liver enzyme called gamma-glutamyl transferase by 2%, 5%, and 15%, respectively.

Specifically, participants who took cafestol lost about 880 grams (g) of weight, while those on the placebo gained 920 g. Those who took cafestol had an average 400-milliliter decrease in visceral fat volume.

Cafestol also seemed to change how fat was processed in the body. The cafestol group exhibited higher initial free fatty acid levels following the intervention, potentially suggesting an undesirable increase in insulin resistance in fat tissues.

The study reported no harmful liver or kidney changes, though one person with infectious mononucleosis (mono) had a slight increase in a liver enzyme. Some people experienced side effects like gas, nausea, loose stools, and mild headaches.

The researchers proposed that while the study showed mixed results, it still might help explain observed associations between coffee consumption and reduced type 2 diabetes risk.

Medical News Today spoke with Thomas M. Holland, MD, MS, a physician-scientist and assistant professor at the RUSH Institute for Healthy Aging, RUSH University, College of Health Sciences, who was not involved in the study.

Holland explained that “cafestol may work by enhancing fat metabolism, leading to weight loss and visceral fat reduction.”

“Its effects on liver enzymes like gamma-glutamyl transferase could indicate improvements in liver health, which is crucial for overall metabolic function,” he said.

However, he suggested that the lower doses or shorter periods of cafestol intake might not have significantly impacted insulin sensitivity in this study due to the insufficient engagement with insulin pathways, which “might explain the lack of more profound effects on glucose metabolism.”

Alyssa Simpson, RDN, CGN, CLT, a registered dietitian and owner of Nutrition Resolution in Phoenix, AZ, who was not involved in the study, highlighted that the findings of the present study were mixed.

She told MNT that “while cafestol appears to aid in weight loss and reduce visceral fat, it also raises concerns due to its potential to increase insulin resistance,” which could raise the risk of developing type 2 diabetes.

She further explained that:

“The rise in free fatty acids observed during insulin sensitivity tests [could] indicate a negative influence on insulin function.”

Both experts emphasized the need for further studies on cafestol’s impact on metabolic health, with Holland suggesting that higher doses or longer interventions might help to clarify its role in diabetes prevention.

Simpson stated that “while the research suggests cafestol might help with fat reduction, it doesn’t strongly support the idea of using coffee to prevent type 2 diabetes in healthy individuals.”

Still, she noted that moderate coffee consumption of 2 to 3 cups per day has been linked to cardiometabolic health benefits in previous research, “so adopting this habit could be part of a balanced lifestyle.”

“For those looking to maximize the health benefits of coffee,” Holland said, “it’s best to consume organic and unfiltered coffee (like French press), since it retains more bioactive compounds like cafestol.”

• avoiding adding sugar or high-fat creamers, as the increased calories and unhealthy fats can negate the potential benefits
• drinking coffee in the morning or early afternoon to avoid sleep disturbances
• grinding coffee beans at home for freshness and higher nutrient content
• using brewing methods that avoid paper filters to help retain more beneficial compounds.

Simpson similarly suggested organic, home-ground coffee if it fits your budget and lifestyle.

She recommends sticking with black coffee or adding small amounts of plant-based or low-fat cow’s milk, avoiding heavy creamers and sugary syrups. If you like your coffee a little sweeter, “natural sweeteners like stevia or small amounts of honey are preferable,” she said.

For those interested in potential cafestol benefits, “decaffeinated coffee might not contain significant amounts of cafestol, as cafestol is primarily found in the oils that remain in unfiltered coffee,” Holland noted.

However, he advised caution for those with health conditions, especially heart conditions like arrhythmia, as caffeine can worsen symptoms.

Additionally, he said that people with autoimmune diseases might be more sensitive to caffeine, potentially experiencing increased fatigue, digestive issues (in irritable bowel conditions), or stress.

The study authors reported a conflict of interest because some are inventors on a patent for using cafestol to treat diabetes, filed by Aarhus University.

According to Mellbye, researchers must inform their institutions about inventions or discoveries made during their work, as per Danish law.

“In our case, after publishing our initial study on cafestol’s effects in cell studies, we informed Aarhus University of our findings,” he explained.

Aarhus University, following the Danish Consolidation Act on inventions from public research institutions, decided to apply for a patent based on the cell research. This led to the patent “Cafestol for treating diabetes,” on which some of the authors of this study are listed as inventors, he said.

“Aarhus University holds the right to the patent,” Mellbye clarified.

If the patent succeeds, investors could receive a share of future earnings. Still, this possible outcome does not necessarily discredit the study’s findings, especially since the results were mixed.