The study, published in the Journal of Endocrinology, also revealed that strength training significantly reduced glucose levels and improved insulin sensitivity in the mice. Given the results of the study, the researchers concluded that strength training can be used to treat diseases linked to obesity, such as Type 2 diabetes and non-alcoholic fatty liver disease (NAFLD).
Non-alcoholic fatty liver disease (NAFLD) is a condition marked by an accumulation of fat around the liver as a result of poor nutrition. As the largest organ inside the body, the liver performs over 500 important functions including energy production, cholesterol metabolism, detoxification and protein synthesis.
A healthy liver should contain little or no fat at all, as fat can make it difficult for the liver to carry out vital functions. Excess fat can also compromise the liver's sensitivity to insulin and impair its ability to regulate glucose levels. An individual is considered to be at risk of NAFLD if more than five to 10 percent of the liver's weight is fat. A fatty liver is also linked to an increased risk of serious conditions like kidney disease, hypertension and cardiovascular disease.
Early-stage NAFLD does not cause symptoms at all, so it often occurs undetected. But over time, NAFLD can lead to serious liver damage and nonalcoholic steatohepatitis, the aggressive form of NAFLD that causes severe inflammation and total liver failure.
Obesity significantly increases the risk of developing a fatty liver. Up to a third of American adults have NAFLD due to poor nutrition alone, and up to 90 percent of people who are overweight are also diagnosed with NAFLD. Individuals who have NAFLD are also often observed to have high cholesterol and triglyceride levels.
But growing evidence suggests that there is a strong link between NAFLD and Type 2 diabetes as well. Excess sugar consumption impairs insulin sensitivity and disrupts the ability of the liver to regulate glucose levels, a complication that NAFLD shares with Type 2 diabetes. Additionally, excess sugar consumption often leads to weight gain and a heightened risk of obesity, which suggests that NAFLD and Type 2 diabetes have a cyclical connection.
Treating NAFLD focuses on reducing or preventing fat buildup around the liver, mainly by addressing underlying causes like high cholesterol and blood sugar levels.
Anaerobic exercises, like strength training, are used by athletes and physical fitness enthusiasts to improve strength, speed and power. Unlike aerobic exercises that boost endurance, anaerobic exercises are mainly used to build muscle mass and improve overall strength. (Related: Strength training, more than walking and cycling, significantly reduces heart disease risk.)
As the Sao Paolo study demonstrated, strength training also has an especially significant effect on liver fat content.
To examine the effects of strength training, the researchers conducted a 15-day experiment on three groups of obese mice. One group followed a standard diet and lived a sedentary lifestyle, the second group followed a high-calorie diet and remained sedentary as well, and the third group followed a high-calorie diet but completed two weeks of strength training.
After 15 days, the researchers observed a significant improvement in the third group's glucose levels and liver fat content. Although the mice were still obese, strength training exercises were able to cut liver fat by up to 30 percent and reduce liver inflammation.
NAFLD and Type 2 diabetes are two of the most common cardiovascular disease-related metabolic disorders. Given its results, the Sao Paolo study offers a natural and holistic treatment for individuals who have fatty livers and Type 2 diabetes.