Being overweight or obese often leads to certain cardiovascular ailments, including hypertension. Individuals who have a high BMI and hypertension usually have other diseases, such as diabetes or high cholesterol, that can worsen hypertension. Controlling your BMI can help control your hypertension.
Body Mass Index
Body mass index is the measurement of body composition that factors in both height and weight. BMI puts you into one of four categories. A BMI under 18.5 is considered underweight. If your BMI is between 18.5 to 24.9, your weight is healthy. A BMI of 25 to 29.9 is overweight and anything over 30 is considered obese.
Blood Pressure
Blood pressure is the measurement of force exerted on the vessel walls. It is represented by two numbers -- systolic pressure and diastolic pressure. Systolic pressure is the amount of force on the heart while it is contracting or beating. Diastolic pressure is the amount of force the heart faces while filling. When written, systolic pressure is above diastolic pressure, and both are measured in millimeters of mercury, or mmHg. Chronic blood pressures over 140/90 mmHg are considered hypertensive.
Theories/Speculation
A BMI in the overweight or obese range can lead to hypertension. In a study published in "Obesity" in 2000 by Clarice D. Brown and colleagues, the effects of BMI on blood pressure were analyzed. This study took a national survey of adults, including their BMI, blood pressure and blood cholesterol. When the results were analyzed, there was a clear link between BMI and incidence of hypertension.
BMI and Systolic Pressure
Systolic blood pressure is affected by the contractility of the arteries. In other words, when the heart beats, the arteries distend and recoil. When the arteries are rigid, systolic blood pressure goes up. Rigidity of blood vessels is affected by body composition and weight. Less compliant blood vessels also means less return of blood to the heart. Generally, in a person with a high BMI, the heart beat is fast because of size and de-conditioning. Less return of blood means that the heart must work even harder to pump the amount of blood that a larger body needs.
BMI and Diastolic Pressure
Diastolic pressure is affected total peripheral resistance around the heart. Total peripheral resistance is the resistance to blood flow and cardiac filling. Large amounts of fat put increased resistance on the arteries of the body, making the diastolic pressure greater.
Prevention/Solution
Lifestyle changes, including diet and exercise, can help reduce BMI and blood pressure. A study published in the "Annals of Internal Medicine" in 2002 by Seamus P. Whelton and colleagues analyzed the effects of aerobic exercise on hypertension. The study found that aerobic exercise was responsible for decreasing blood pressure in hypertensive, overweight individuals. A low-fat, low-sodium diet full of fiber, fruits, vegetables and whole grains can be effective at lowering both blood pressure and body weight.
References
- "Anatomy and Physiology"; Saladin, Kenneth S.; 2004
- Nature.com: Body Mass Index and the Prevalence of Hypertension and Dyslipidemia
- "Exercise Physiology"; Brooks, George A., Fahey, Thomas D., Baldwin, Kenneth M.; 2005
- Annals of Internal Medicine; "Effect of Aerobic Exercise On Blood Pressure - A Meta Analysis of Randomized Control Trials" Seamus P. Whelton, et.al; 2002
- National Heart Lung and Blood Institute: Calculate Your BMI
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