Body weight and blood pressure regulation
High blood pressure is the most common chronic disease in North America today, and perhaps the most easily prevented. It has been estimated that the excess weight of the U.S. population is over one million tons. Put another way, the average American is 4.5kg (10 lbs) overweight. Yet the loss of just 10 pounds weight could normalize the blood pressure of many of the 50 million Americans who now suffer from hypertension, greatly reducing their risk of heart disease, renal failure and stroke.
As many as half of the adults now being treated with drugs for high blood pressure could dramatically cut or even eliminate their need for medication with just a modest drop in body weight. The gains from weight loss are substantial and they come quickly; in fact, the fastest drop in blood pressure comes at the start of a period of weight loss, and is already evident after just two or three weeks.
Few relations between behaviour and illness are so established or so stark as that between weight and blood pressure. Regardless of sex, age or race, obesity is the foremost contributing factor to hypertension. Among adults aged 20 to 45, obese individuals are five to six times more likely to be hypertensive than lean individuals, and the earlier obesity appears, the greater the disparity. Adolescent or childhood obesity is a forewarning of adult hypertension, cardiovascular disease, high cholesterol and high mortality.
A 1992 study of 800 men and women with mild hypertension demonstrate show weight loss can affect blood pressure. After six months, patients who had lost less than 2.25 kg (5 lbs) showed an average drop in diastolic (heart-dilated) blood pressure of 7 mmHg. Those who had lost 4.5 kgs (10 lbs) had dropped 11.6 mmHg. Even larger drops were seen in hypertensive patients also taking medication.
It is not clear exactly why weight reduction has such a startling effect. The increased exercise usually involved in losing weight may well be a factor. But it is now known that body mass index, the scale that doctors use to determine obesity, has more impact on hypertension than sodium intake, stress, or any other commonly-blamed factor.
While the effect of losing weight is most dramatic in seriously overweight hypertensive patients, even thinner people with high blood pressure can bring it down by losing a few extra pounds, though there does seem to be a point at which blood pressure ceases to fall in line with weight.
Of course, it is fat and not weight itself that causes blood pressure to rise. A bodybuilder may be well over the ideal body weight for his height because of large muscle mass, but that doesn’t mean that he is in grave danger of hypertension. It is the percentage of body weight that consists of fat, and not just the gross weight of the body, that most affects blood pressure.
The distribution of fat on the body also plays a role. Centripetal fat, the fat that is deep inside the body rather than close to the skin, is particularly associated with hypertension. Doctors can measure fat distribution by comparing the circumference of the waist with the circumference of the hips. High waist-to-hipratios, or pot-bellies, are not only a strong indicator of hypertension, but of stroke and ischemic heart disease too.
Burning off that fat is better than simply eating less. The best results, not only in lowering blood pressure but also in reducing plasma lipid levels, come from weight loss achieved through diet and exercise, rather than by diet alone. Best of all, the drop in blood pressure that comes with weight reduction is permanent. As long as you keep the weight off, you can keep hypertension in check and take some of the weight off your arteries for good.
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