An article from Norwegian SciTech News at NTNU

Losing weight is fine if you want to reduce your risk of heart attack. But you don’t necessarily reduce the risk of other heart problems if you only start focusing on fitness later in life. (Illustrative photo: Colourbox)
Losing weight is fine if you want to reduce your risk of heart attack. But you don’t necessarily reduce the risk of other heart problems if you only start focusing on fitness later in life. (Illustrative photo: Colourbox)

Overweight youths at greater risk for heart failure

A high BMI when you’re young increases the risk of heart failure, even if you’re dieting away the pounds as you get older. Yo-yo dieting is the worst.

Gemini, NTNU Trondheim - Norwegian University of Science and Technology

NTNU is the second largest of the eight universities in Norway, and has the main national responsibility for higher education in engineering and technology.

It comes down to starting healthy habits early. Fortunately, it’s never too late to adopt a healthier lifestyle, and losing weight is great for reducing your risk of heart attack. But you can still be at a higher risk for other heart problems if you’re late in changing your habits.

Excessive weight at a young age puts one at a far higher risk of heart failure as compared with maintaining a healthy weight throughout one’s life. Even slight overweight increases risk by 45 per cent as compared with normal weight. (See fact box.)

Researchers fear that the obesity epidemic will lead to more cases of heart failure even if younger people with obesity are able to adjust their weight later in life.

“If the current trend continues, 60 per cent of the world’s population will have a BMI in the overweight or obese range by 2030,” says NTNU professor Imre Janszky of the Department of Public Health and General Practice.

Risk of heart attack Even when taking into account differences in age, smoking, socioeconomic factors and physical activity level, people who were slightly overweight for 30 years (BMI of 25 to 27.5) had a 17 per cent greater risk of heart attack as compared with those in the normal weight range and with average BMI. Individuals who were morbidly obese for 30 years had a 66 per cent increased risk. 

Risk of heart failure: The risk of heart failure increased by 45 percent in slightly overweight individuals, was approximately double in those with persistent obesity, and was about four times greater when the average BMI was higher than 35 for 30 years.

Especially worrisome is the increasing incidence of obesity in children, he says.

“Since our study results suggest that obesity is a major risk factor for both heart attacks and heart failure, the obesity epidemic has considerable significance for the scope of these diseases,” says Janszky.

Average BMI is most important

Between 1966 and 1969, residents in Nord-Trøndelag were weighed and measured in conjunction with a mass tuberculosis screening.

More than 26,000 of the same individuals also participated in both the second and third Nord-Trøndelag Health Studies (HUNT) in the mid-1980s and mid-1990s.

Heart failure occurs when the heart is not able to pump blood around the body strongly enough for all organs to receive an adequate blood supply. The most typical symptoms are shortness of breath and impaired physical performance, and eventually leg swelling may develop.

Heart attacks occur when a blood clot blocks one of the coronary arteries, preventing the supply of blood and oxygen to part of the heart. The heart is damaged after a few minutes, and if the blood supply is cut off for a longer time, the part of the heart not getting blood dies. The dead tissue creates the actual attack.

Whereas a person’s most recently measured BMI value was the one most strongly associated with the risk of getting a heart attack, the risk of heart failure, by contrast, corresponded more strongly with a person’s average BMI over a period of 30 years.

The study, recently published in the Journal of Internal Medicine, revealed that a high BMI earlier in life increased the risk of heart failure even when researchers adjusted the analysis for the most recent BMI measurement.

“The findings indicate that persistent obesity affects the heart over time, and that BMI in early life is an important factor that can increase the risk of heart failure in middle age,” says Janszky.

For heart attacks, however, the most recent BMI measurement was the most important factor, which may indicate that it is never too late to lose weight if you want to reduce your risk of acute myocardial infarction.

HUNT study statistics

By the end of 2008, 1851 of the 26,000 Norwegians in the HUNT Study had experienced a heart attack, and 946 had heart failure. Higher BMI was associated with an increased risk of both heart attack and heart failure, and obesity was associated with a particularly high risk for heart failure.

The risk increased even after the researchers had adjusted the analyses for gender, age, smoking, alcohol consumption, education level, marital status and physical activity.

“When we then also adjusted for metabolic status, the relationship between BMI and heart attack was no longer significant, which indicates that the metabolic consequences of overweight and obesity appear to have the greatest impact for heart attacks,” says Janszky.

In plain speak, this means that a high BMI is not the direct cause of a heart attack, but that overweight and obesity increase the risk of high blood pressure, high blood sugar and an unfavourable blood fat profile, which in turn increase the risk of heart attack.

These factors, however, could not explain the correlation between high BMI and heart failure, which may indicate that obesity itself weakens the heart.

Stable weight may be best

The researchers also examined how changes in body weight over time were associated with future heart failure. Study results showed that weight loss and weight gain were both associated with increased risk.

Those who maintained a stable weight throughout all three measurement periods had a lower risk than those whose weight fluctuated.

“There was a particularly strong increase in risk for people whose mid-1980s BMI varied from their other two measurements. This may indicate that yo-yo dieting involves additional risks,” says Janszky, although he stresses that this interpretation is just based on a single BMI measurement between the first and last measurements.

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