For millions of overweight individuals, one of the potentially harmful consequences of the excess pounds is an increased risk of hypertension (high blood pressure). As anyone who has ever struggled with this problem can attest, losing weight and keeping it off is an ongoing effort. But it's a crucial step, say some US scientists, who reported that weight loss helped a group of people with hypertension lower their blood pressure, some to a normal, healthy range. The findings appear in the journal Preventive Medicine.

Link between weight and blood pressure

The researchers collected data on several thousand participants of an ongoing study of heart disease. All were between the ages of 45 and 64, and all had hypertension that measured 140/90 mmHg or higher. The participants' blood pressure readings, weight, and waist measurements were recorded annually over a 9-year period. The researchers were looking for a connection between changes in weight and waist circumference and changes in blood pressure.

The effect of weight loss

Unfortunately, most of the people gained weight during the study, but those who were able to lose some weight saw favorable changes in their blood pressure. People who lost more than 3 kg (6.6 lbs) over the 9-year period were more than twice as likely as others to end the study with normal blood pressure readings. Even a weight loss of less than 3 kg was associated with lower blood pressure readings. And in the 45- to 55-year-old age bracket, those who were able to slim their waistlines were more likely than others to end the study with normal blood pressure readings.

On the other hand, participants who gained more than 6 kg (13 lbs) over this time were much more likely to have high blood pressure at the end of the study. Among those over 55, reductions in weight and abdominal fat did not have as great an effect on blood pressure readings.

How weight loss helps

It's not yet clear why weight loss works so effectively to lower blood pressure, but the authors of the study say that losing some body fat probably makes it easier for the heart to pump blood through the smaller blood vessels. They speculate that weight loss also helps to limit sodium retention and improve the body's ability to utilize insulin - both steps that contribute to better blood pressure control.

The authors also cannot fully explain why weight loss seemed to benefit the younger participants more than it did the older ones. It's possible that long-term hypertension is more difficult to treat. They also say that the weight changes seen in the older individuals may represent the loss of muscle mass rather than fat. That would limit the effect that weight loss would have on hypertension.

Weight control part of the solution

If you are overweight and have hypertension, you probably already know that losing weight can help manage the condition. Medications can help, as well, but attention to lifestyle factors - including diet and exercise - are an essential part of your treatment plan. And unlike medication, lifestyle measures do not have side effects, which can be unpleasant. As this study illustrates, even modest changes in body weight and activity level can have a measurable effect on high blood pressure.