Higher levels tied to lower body fat, diabetes risk

For the study, the researchers examined data that came from a genome-wide association meta-analysis of 9,876 individuals of mostly European ancestry.

They used the data to examine two common genetic variants — CYP1A2 and AHR genes — in their analysis. These genes slow down caffeine metabolism, meaning that for those carrying the variants, less coffee needs to be drunk in order to have elevated levels of caffeine in their blood, compared to those who metabolize it quickly.

Researchers also collected data on body fat, type 2 diabetes risk, and risk for cardiovascular conditions.

In the end, the researchers found that genetically predicted higher blood levels of caffeine were linked to lower BMI, whole body fat mass, and type 2 diabetes risk.

Through further analysis, they found that 43% of the protective effect of blood levels of caffeine on type 2 diabetes came from weight loss.

They found no strong link between genetically predicted caffeine levels and cardiovascular conditions, including ischemic heart disease, heart failure, and stroke.

When asked how higher caffeine intake may increase weight loss, Dr. Dana Ellis Hunnes, assistant professor at UCLA Fielding School of Public Health, who was not involved in the study, noted that higher caffeine intake increases thermogenesis, or heat production, in the body.

She explained for Medical News Today that “[h]eat production increases calorie burn, and when we burn more calories than we take in, we are more readily able to lose weight and fat.”

Dr. Rohini Manaktala, a cardiologist at Memorial Hermann in Houston, TX, not involved in the study, also told MNT that caffeine causes weight loss by speeding up metabolism.

“This is a dose-dependent process, meaning [that] increasing [the] intake of caffeine […] leads to more fat and calorie burning, which is reflected in weight reduction,” she explained. “Caffeine also inhibits overindulgence in eating by suppressing an individual’s appetite resulting in calorie deficiency which helps in preventing weight gain.”

MNT also spoke with Dr. Mark Guido, an endocrinologist with Novant Health Forsyth Endocrine Consultants in Winston Salem, NC, not involved in the study, to understand how, besides weight loss, caffeine may reduce type 2 diabetes risk.

He said that the science is “mixed” on the topic, but that caffeine may reduce type 2 diabetes risk by altering how the body uses glucose and insulin.

The researchers concluded that higher blood levels of caffeine might lead to weight loss and reduce type 2 diabetes risk.

Dr. Guido noted that the study has significant limitations. He said: “It looked at naturally elevated caffeine levels in people with a certain genetic predisposition, and it does not appear to look at elevated caffeine levels from food or drink. There is a question if these findings would be relevant to increased caffeine levels from food or drink.”

He added that the study only looked at reducing the risk of developing type 2 diabetes as opposed to how caffeine affects those already with the condition.

Dr. Hunnes noted that the results are “not really causal in nature,” as unlike a randomized controlled clinical that studies the “whole person,” it merely studied the effects of genomes.

“It’s sort of like looking at in vitro — in [a] test tube — issues and making assumptions about how it will react in a person,” she noted.

Dr. Manaktala added: “A more robust randomized control study would be beneficial in studying the true clinical and health effects of caffeine. Moreover, the study participants were of European descent. This makes it challenging to extrapolate study findings to the general population in the U.S.”

Dr. Manaktala called the findings “exciting,” and noted that they mean a “healthy dose” of caffeine may help prevent obesity, a major risk factor for cardiovascular conditions. However, she noted:

“[W]e need to exercise caution before completely accepting the study’s findings and adopting new dietary habits. Most importantly, what we need to remember is that caffeine cannot be a substitute for leading a healthy lifestyle which includes, eating plenty of fruits, vegetables, lean meats, and a moderate intake of carbohydrates/ fats along with daily moderate-intensity physical exercise and careful management of chronic conditions that are risk factors for heart disease.”

Dr. Guido noted that he would not make any different recommendations to his patients based on the study findings.

“I think it is interesting and further studies likely need to be done, but at this time, I don’t think it changes anything regarding recommendations for the prevention of type 2 diabetes,” he said.

“I would not alter caffeine intake based on this study,” he repeated. “It only looked at people with naturally high caffeine, not how much they get from food or drink.”

“We also know that too much caffeine can also have significant harmful effects on health with regard to elevated blood pressure and poor sleep, and in patients who already have type 2 diabetes, caffeine can make their sugars worse,” cautioned Dr. Guido.