A recent study reveals that losing fat without reducing muscle mass results in a significantly lower risk of heart failure in people with type 2 diabetes.
In the United States, around 1 in 10 people have diabetes, and 90–95% of them have type 2 diabetes. Type 2 diabetes usually develops after age 45. Estimates suggest that by 2045, 700 million adults worldwide will have this condition.
Type 2 diabetes usually begins as insulin resistance. This is a condition wherein the body’s cells no longer react to the insulin the pancreas produces to control blood sugar.
Genetics, ethnicity, and advancing age all play a role in the development of insulin resistance and diabetes. However, excess weight, a lack of exercise, an unhealthful diet, and smoking may be driving factors in its occurrence.
Once doctors diagnose this condition, the primary treatments they advise generally include taking medications and making certain lifestyle changes, such as losing weight and improving the diet.
As diabetes nearly doubles the risk of death due to heart disease or stroke and increases the risk of having heart failure by a factor of two in males and five in females, many researchers are focusing on preventing these and similar health complications for those with diabetes.
Heart failure, or congestive heart failure, occurs when the heart muscle does not pump the blood adequately. This leads to a buildup of fluid in the lungs or legs, or sometimes both.
Heart failure has a number of potential causes. For example, after a heart attack (when the heart muscle sustains damage due to a lack of oxygen), the muscle is weak and cannot pump well.
Heart failure can also occur due to type 2 diabetes. This is as a result of direct harm to the heart muscle from raised blood sugar and systemic inflammation associated with the condition.
One prevention strategy includes weight loss for people with overweight or obesity. However, not much is known regarding what type of weight loss has the most impact on reducing the risk of diabetes-related heart issues.
The study
To investigate this further, researchers at the University of Texas Southwestern Medical Center (UTSW) in Dallas analyzed data from the Look AHEAD study.
This is a randomized trial investigating weight loss due to intensive lifestyle intervention, consisting of healthful eating and increased physical activity versus support and education alone in people with type 2 diabetes.
The UTSW research, which appears in the journal Circulation, received funding from the National Heart, Lung, and Blood Institute, the Texas Health Resources Clinical Scholars Program, and the National Institutes of Health (NIH).
The researchers selected 5,103 people from the Look AHEAD study who did not have heart failure at the beginning of the study. The participants also had sufficient baseline measurements needed for prediction equations to estimate how much fat mass and lean (muscle) mass they had.
Data on the participants’ weight and waist circumference were available at the beginning of the study and over a 4-year period. The team also noted hospitalizations for heart failure over a 12-year time frame.
During the trial’s 12-year follow-up, 257 study participants were hospitalized for heart failure treatment.
In the Look AHEAD study, scientists used a scanning technique called dual-energy X-ray absorptiometry (DXA) to determine body composition in a subset of about 1 in 5 of the participants. These participants also had information recorded on factors such as height, weight, waist circumference, and ethnicity.
This meant that the researchers could validate existing equations that predict the proportion of fat mass and lean mass from these factors, which are simple to collect compared with the much more complicated process of conducting a DXA scan.
The researchers’ analysis of the subset of participants with DXA scans provided a new equation specific to this study group. They applied this new equation to the remaining participants without a DXA scan to accurately predict their fat mass and lean mass.
This revealed that adults in the study who had lost weight were less likely to develop heart failure if they lowered their fat mass and waist circumference. However, losing lean mass did not change their risk.
The investigators note that although the risk of heart failure decreased in those who lost body fat and reduced their waist circumference, the study data showed no significant reductions in heart attack risk.
The team also considered the participants’ ejection fraction (EF) ratio. This is a measurement of the amount of blood leaving the heart with each contraction.
The data showed that reducing body fat mass by 10% resulted in a 22% lower risk of heart failure with preserved EF ratio and a 24% lower risk of heart failure with reduced EF ratio.
“Our study suggests that simply losing weight is not enough. We may need to prioritize fat loss to truly reduce the risk of heart failure.”
– Study co-author Dr. Kershaw Patel, a cardiologist at Houston Methodist Hospital in Texas
Supporting evidence
A study from May this year, which appears in the journal Circulation Research, compared obesity phenotypes, diabetes, and cardiovascular diseases.
The comparison suggests that some people who have a healthy weight or overweight but an excess amount of fat deposits around the internal organs and under the skin have a higher risk of diabetes and heart disease.
The researchers say that it is not possible to determine the risk of cardiovascular disease and type 2 diabetes based on body mass index (BMI) alone — mostly because body composition is so diverse.
They suggest that since excessive amounts of fat tissue largely define cardiovascular risks, reducing body fat is critical for prevention.
Implications and limitations
The results of the UTSW study suggest that for people with diabetes who also have overweight, losing weight, in general, may not be adequate to reduce heart health risks.
If further studies replicate these findings, it could confirm that losing weight by shedding visceral fat from around the organs — rather than losing muscle mass — is a key factor when it comes to reducing the risk of heart failure in type 2 diabetes.
The study authors also say that further investigation is necessary to determine if building or maintaining muscle in addition to losing fat mass would be even more effective in reducing the risk of diabetes-related heart failure.
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