A weight training component to your exercise routing is critical to reducing belly fat, according to new research coming out of the Harvard School of Public Health. Belly fat tends to become more stubborn as we age, it is easier to gain and harder to lose. This led researchers at Harvard to look at ways to help get rid of the stubborn fat that can be hazardous not only to the waistline but also to heart health.

Researchers found that the combination of aerobic exercise and weight (or resistance) training is the formula for reducing belly fat. Author of the study Rania Mekary, who is also a researcher with the department of nutrition at Harvard, says that “engaging in resistance training or, ideally, combining it with aerobic exercise could help older adults lessen abdominal fat while increasing or preserving muscle mass”.

The study was performed between 1996 and 2008, and was comprised of over 10,000 men around the age of 40. These men were in healthy condition at the beginning of the study and had widely varying body mass indexes (BMI), which is an equation that takes height and weight into account to determine a healthy mass range for a person.

The study placed much of the focus on the waistline, as this is the area that has been shown to have correlation between increased fat and risk for heart disease. Researchers were looking to find which exercises showed the most promise in decreasing or preventing harmful belly fat.

Through the study, the researchers found that those men with declining physical activity (in terms of actual exercise) over the 12 year period were more likely to see a BMI increase. Men who averaged 20 minutes of exercise that included weight or resistance training coupled with aerobic activity saw a much smaller increase in belly fat over the course of the study.