TUESDAY, June 25, 2013 – The elevated body mass index (BMI) in overweight and obese people isn’t just linked to heart failure, it actually causesheart failure, finds a major new genetic study.

Normal BMI is from 18 to 25. But for every one-point increase in BMI over 25, the incidence of heart failure goes up 17 percent in overweight people, according to the large-scale, international study of 200,000 people. This calculation means an estimated 113,000 new cases of heart failure yearly in the United States for each one-unit increase in BMI.

The international research project brought together 35 studies and more than 130 authors from the ENGAGE (European Network for Genetic and Genomic Epidemiology) Consortium, led by Dr. Tove Fall of the Karolinska Institute in Uppsala Sweden in collaboration with Oxford University in the United Kingdom. Published today in PLOS Medicine, the research sheds new light on causes of cardiovascular disease, currently the No. 1 killer in the United States.

“We know now that increased adiposity [fat] in itself is dangerous to the heart,” said study investigator Dr. Fall. Before, researchers knew there was a link, but couldn’t find a direct cause-and-effect relationship.

The relationship has to do with connections to the human gene for obesity, known as FTO (fat-mass and obesity-associated gene) which makes people susceptible to obesity and has to do with appetite. The FTO gene accounts for a third of all the variation we see in people’s weights as increased BMI. Scientists observed that if you have one copy of the gene, you weigh more than if you have no copies, and if you have two copies of the gene, weight is even higher in large population studies. Now, increased BMI is connected to 24 cardio-metabolic traits related to heart diseases, in this new study.

Researchers found that higher BMI in overweight and obese patients actually caused heart failure, possibly due to increased blood pressure and stress on the heart organ. Elevated BMI also caused higher than normal levels of liver enzymes that indicate fatty liver disease. In addition, high BMI was linked to:

  • Heart failure
  • Stroke
  • Hypertension
  • Dyslipidemia (high cholesterol)
  • Metabolic syndrome (a precursor to diabetes)
  • Type 2 diabetes
  • Higher risk for death

This is particularly concerning because obesity is on the rise around the world.

“This large study provides a more direct link to heart disease using genetic information,” said Stephanie Moore, MD, a cardiologist at the Massachusetts General Hospital (MGH) Institute for Heart, Vascular and Stroke Care’s Heart Failure and Cardiac Transplant Program in Boston.

Take Control of Your Jean Size, Not Your Genes

While this has established the relationship between overweight and heart disease, it leaves an important question for future studies — whether losing weight will reverse a heart condition. “If we normalize our BMI,” said Dr. Moore, “we have less cardiac risk factors like diabetes, high blood pressure.”

While most experts agree that reducing risk factors should translate into fewer cases of heart disease, Moore was more cautious. “We would have to follow these patients in this study longitudinally, or over time, to truly prove that reducing your BMI with genetic predisposition decreases risk,” she said.

Dr. Moore counsels her patients about their genetics and taking control over their weight. “I do tell my patients, you can’t change your genes, but you can change your jeans size,” said Moore.

To find your own BMI, divide your body weight by your height, using our BMI calculator.

According to study investigator Fall, “This is important, because this means that targeting an optimal BMI through various strategies will reduce the risk of having heart failure.”

Fall points out that there is more to be done, to answer the question of whether weight loss will impact the heart directly. “We only studied the effect of adiposity [fat] on a population level,” he said.

But, he added, “However, since we know that weight loss will improve many of the CVD [cardiovascular disease] risk factors and decrease the workload on the heart, it is very plausible that weight loss will decrease the risk of CVD.”

“The most important prescription I can’t write is for weight loss,” said Moore — acknowledging that weight loss is challenging for both physicians and patients.

What can you do to bring your BMI into a healthy range if it’s not?

“I refer patients routinely for weight reduction surgery or weight loss programs,” said Moore. A healthy diet plays an important role in heart health too. “Vegetables, lean meats, fruit and daily exercise are the best bet to avoid heart disease,” she added.