Losing weight is proven to lower blood pressure, and low-carbohydrate diets (such as the Atkins diet) may be better at lowering high blood pressure than low fat diets, according to US research.

Extra weight raises your blood pressure

It is well known that your weight and body shape affect your blood pressure and risk of developing heart disease and strokes. The general rule of thumb is: the greater your weight, the higher your blood pressure.

Everyone with high blood pressure (or higher than normal blood pressure) is advised to try to keep to a healthy weight to keep their blood pressure under control.

A big stomach puts pressure on your heart

Often the extra weight is put on as fat around the stomach (known as abdominal fat). And it is these extra abdominal pounds that appear to be the cause of the problem. The stomach tissues release hormones and chemical messengers that raise your blood pressure by affecting the heart and kidneys.

It's better to be a pear than an apple

This is why people who are apple-shaped (who put on weight around their stomachs) are more likely to develop heart disease and strokes than people who are pear-shaped (who put on weight around their hips and thighs).

Low-carbohydrate diets may work better than diets using fat-removal pills at lowering blood pressure

This US study compared two different methods for lowering blood pressure by losing weight - eating a low-carbohydrate diet (Atkins-style diet) or using a fat-removing weight loss pill (orlistat - also known as Alli or Xenical). It found that, while both produced equal amounts of weight loss, the low-carbohydrate diet appeared to produce a greater lowering of blood pressure.

The study followed 146 obese or overweight people for almost a year as they tried to lose weight using one of the two methods.

Most of the weight loss in both groups of dieters happened in the first 12-24 weeks, with their maximum weight loss achieved after 24-36 weeks. After 36 weeks there was a slight regain in weight.

Although both groups lost equal amounts of weight, the results of the small study showed that the low-carbohydrate diet was better at lowering blood pressure:

• Systolic (top) blood pressure lowered by 5.9mmHg and diastolic (bottom) blood pressure lowered by 4.5mmHg for the low-cardohydrate diet group
• Systolic (top) blood pressure increased by 1.5mmHg and diastolic (bottom) blood pressure increased by 0.4mmHg for the fat-removing weight loss pill group.

Reference: Yancy Jr WS, Westman EC, McDuffie JR et al. A Randomized Trial of a Low-Carbohydrate Diet vs Orlistat Plus a Low-Fat Diet for Weight Loss. Archives of Internal Medicine 2010;170(2):136-145