Body weight is a determinant of blood pressure at all age; in fact:
- it has been estimated that the risk of developing elevated blood pressure is two to six time higher in overweight than in normal-weight individuals;
- there is a linear correlation between blood pressure and body weight or body mass index (BMI) (a BMI greater than 27, i.e. overweight or obesity, is correlated with increased blood pressure): even when dietary sodium intake is held constant, the correlation between change in weight and change in blood pressure is linear;
- 60% of hypertensives are more than 20% overweight;
- centripetal distribution of body fat (waist circumference greater than 34 inches in women and 39 inches in man), also associated with insulin resistance, is more important determinant of blood pressure elevation than that peripherally located in both man and women;
- it has been shown that weight loss, both in hypertensive and normotensive individual, can reduce blood pressure and reductions occur before, and without, attainment of a desirable body weight.
In view of the difficulties of sustaining weight loss, efforts to prevent weight gain among those who have normal body weight are critically important.
How to calculate BMI
BMI is total body weight, expressed in kilograms [kg] or pounds [lb], divided by the height squared, expressed in meters or inches (in.).
It can be calculated using the following equations:
BMI = weight [kg]/height2 [m] or
BMI = (weight [lb.]/heigth2 [in.]) x 705
BMI is a good indication of body fat because most of the weight differential among adults is due to body fat; its major flaw is that some muscular individuals may be classified as obese even if they are not.
A healthy BMI is between 18 to 24,9.
Overweight is considered to be between 25 to 29,9.
Obesity is categorized by BMI according to three grades:
- 30 to 34,9 I grade obesity;
- 35 to 40 II grade obesity:
- 40 and above III grade obesity.
Physical activity, and blood pressure
Maintaining a high level of physical activity is a critical factor in sustaining weight loss.
In addition to the effect on body weight, activity and exercise in itself reduce the rise in blood pressure.
Physical activity produces a fall in systolic blood pressure and diastolic blood pressure; so, increasing physical activity of low to moderate intensity to 30 to 45 minutes 3-4 days/week up to 1 hour nearly every day, as recommended by World Health Organization, is important for the primary prevention of hypertension.
Less active persons are 30% to 50% more likely to develop hypertension than active ones.
Remember: a rolling stone gathers no moss!
Writing Group of the PREMIER Collaborative Research Group. Effects of comprehensive lifestyle modification on blood pressure control: main results of the PREMIER Clinical Trial. JAMA 2003;289:2083-2093. doi:10.1001/jama.289.16.2083
World Health Organization, International Society of Hypertension Writing Group. 2003 World Health Organization (WHO)/International Society of Hypertension (ISH) statement on management of hypertension. Guidelines and recommendations. J Hyperten 2003;21:1983-92.