Slight Weight Gain Found to Increase Heart Failure Risk
Cardiologists have long known that obesity increases the risk of death from heart failure, but a new study shows that being even slightly overweight--as little as four pounds over--also increases the risk substantially.
That increased risk, furthermore, arises from being overweight itself rather than from fat’s effect on hypertension and diabetes. A 15-year study on nearly 6,000 people shows that being overweight alone is responsible for 11% of cases of heart failure in men and 14% of cases in women, a team from the Boston University School of Medicine reports in today’s New England Journal of Medicine.
“Most of the time, we think of extreme obesity as a cause of heart failure,” said Dr. Robert H. Eckel of the University of Colorado Health Sciences Center, a spokesman for the American Heart Assn. “But these people were not extremely obese.... This is another good reason to lose weight. And even if you can’t lose weight, don’t gain any more because that would put you in a higher risk group.”
The new findings are alarming because obesity has reached “epidemic levels” in the United States and is still increasing, said Dr. Claude Lenfant, director of the National Heart, Lung and Blood Institute, which sponsored the study.
An estimated 61% of adults in this country are considered overweight, according to the study. In particular, 13% of young children and 14% of adolescents are now overweight.
“The results of this study are a wake-up call to a public health problem that we may be addressing 10 to 50 years from now when these obese youngsters become old enough to be at risk of heart failure,” said Dr. Daniel Levy of Boston University.
An estimated 2 million to 3 million Americans suffer from heart failure, which occurs when the heart is unable to pump sufficient blood to meet the body’s needs. Symptoms include shortness of breath, fatigue and edema (water retention) in the ankles and feet. High blood pressure and diabetes are major risk factors for heart failure. In such cases, the walls of the left ventricle--the heart’s main pumping chamber--get thicker and the heart gets flabby and weak, making it difficult to climb stairs, or even to tie one’s shoes.
The death rate from heart failure, moreover, has remained constant over the last four decades, even while the death rate from heart disease has dropped by 60%, Lenfant noted.
The new results were obtained from the participants of the Framingham Heart Study, a landmark epidemiological study that began in 1948.
Dr. Ramachandran S. Vasan of Boston University and his colleagues followed 5,881 men and women for 15 years, monitoring their weight and the development of heart failure. One-third of the women and half the men were overweight. About 16% of both sexes were considered obese.
“The debate has been whether it is obesity or other factors associated with it that is causing the risk,” said Dr. Greg Fonarow of the UCLA School of Medicine. “What this study is trying to get at is whether obesity in and of itself is a true risk and a true contributor to the development of heart failure. According to them, it is.”
A limitation of the study was that virtually all of the participants were Caucasian. Obesity is a major problem among other ethnic groups, but this study was not able to address those issues.
The team grouped the subjects by their body mass index or BMI, which is the person’s weight in kilograms divided by the square of their height in meters. A BMI calculator is available at www.nhlbisupport.com/bmi/bmicalc.htm. People are considered normal if their BMI is less than 25, overweight if it is from 25 to 29.9 and obese if it is 30 and above.
The team concluded that, independent of all other factors, each 1-point increase in BMI caused a 5% increase in risk for men and a 7% increase for women. For an individual who is 5 feet 10 inches tall, a 1-point increase is equal to 6 pounds.
Overall, they concluded, the risk of heart failure was 34% higher in those who were overweight and doubled in those who were obese.
“Even after we accounted for the effects of all the other risk factors, there was an independent effect of adiposity [being overweight] on heart failure,” Vasan said.
Heart failure is “a grim prognosis, a bad condition to have,” he said. “This should be an impetus for people who do not have an optimal BMI to move in that direction.”
The team is not sure how obesity increases the risk, Vasan added. Some laboratory studies have shown that obese rats, for instance, have deposits of fatty particles in heart muscle cells that lead to cell death, a phenomenon called lipotoxicity. Or, he added, the extra weight may simply make the heart work too hard.
Eckel cautioned that other factors are even more important in raising the risk of heart failure, including age, a previous heart attack, valve disease and high blood pressure. This combination of factors can raise the risk much higher in the obese.
“But it is important for people to realize that you can’t do anything about age, heart attack and valve disease, but you can do something about high blood pressure and you can do something about weight,” he said.
“We know that diet and exercise are beneficial for a variety of reasons,” Fonarow concluded. “The suggestion from this study is that they may also be able to lower the risk of heart failure.”
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Normal or Overweight?
Weight ranking according to the body mass index, which relates weight to height (find your height along the left axis, then move to the right to find your weight). The index may overestimate body fat for athletes or those with muscular builds and under-estimate body fat in older persons:
HEIGHT Body Weight Over-
5 feet Normal------------------------------------- weight Obese
0 97 102 107 112 118 123 128-152 153+
1 100 106 111 116 122 127 132-157 158+
2 104 109 115 120 126 131 136-163 164+
3 107 113 118 124 130 135 141-168 169+
4 110 116 122 128 134 140 145-173 174+
5 114 120 126 132 138 144 150-179 180+
6 118 124 130 136 142 148 155-185 186+
7 121 127 134 140 146 153 159-190 191+
8 125 131 138 144 151 158 164-196 197+
9 128 135 142 149 155 172 169-202 203+
10 132 139 146 153 160 167 174-208 209+
11 136 143 150 157 165 172 179-214 215+
6 feet
0 140 147 154 162 169 177 184-220 221+
1 144 151 159 166 174 182 189-226 227+
2 148 155 163 171 179 186 194-232 233+
3 152 160 168 176 184 192 200-239 240+
4 156 164 172 180 189 197 205-245 246+
BMI 19 20 21 22 23 24 25-29 30+ * Source: National Institutes of Health
