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Obesity induced hypertension

February 10, 2021
Obesity refers to an excessive amount of body fat. It is caused by an imbalance between energy intake and expenditure. As per medical standards, obesity is measured in terms of body mass index (BMI). BMI is a measure of body fat based on the weight and height of a person. BMI= Kg (Weight in kilogram) /m2 (height in meters squared) Obesity is rapidly becoming a major threat to global health. It is ranked as the sixth most important risk factor contributing to the overall disease burden. Obesity-related hypertension is paralleled by an alarming increase in the incidence of various metabolic diseases like stroke, ischemic heart disease, and renal dysfunction, which can lead to a decline in the life expectancy.

What is Hypertension?

Hypertension or high blood pressure refers to a condition, in which the force of blood against the inner walls of the arteries is too high. The higher the blood pressure, the harder the heart has to pump. Based on the recent American Heart Association (AHA) guidelines, blood pressure can be classified as follows:
  • Normal: Systolic pressure less than 120 mmHg and diastolic pressure less than 80 mmHg
  • Elevated: Systolic pressure between 120-129 mmHgand diastolic pressure less than 80 mmHg
  • Hypertension:
    Stage 1 : Systolic pressure between 130-139 mmHgor diastolic pressure between 80-89 mmHg.
    Stage 2: Systolic pressure at least 140 mmHgor diastolic pressure at least 90 mm Hg.
  • Hypertensive crisis: Systolic pressure over 180 mmHg and/or diastolic pressure over 120 mmHg, where patients need immediate care and hospitalization.
According to WHO, hypertension is a major cause of premature death  and affects 1 in 4 men and 1 in 5 women worldwide. It can increase the risk of heart, brain, kidney and other diseases. According to the famous Framingham Heart Study, obesity is responsible for 26% of cases of hypertension in men and 28% in women.

Types of Hypertension

Based on the cause, hypertension is of two types:

  1. Primary (Essential) hypertension: The exact cause of primary hypertension is poorly understood. It may develop gradually over many years due to environmental and genetic factors.
  2. Secondary hypertension: It is the result of multiple etiologies, including renal, vascular, and endocrine causes.

Obesity-related hypertension: Mechanism

Obese individuals have high amounts of fat deposits on the inner walls of the arteries that supply blood. These deposits can narrow the passage, thereby reducing the blood flow. In such cases, heart will pump harder to supply blood to different parts of the body, thus it increases the blood pressure.

The Framingham Study demonstrated that obese individuals have 16 mmHg higher systolic blood pressure and a 9mmHg higher diastolic blood pressure than persons with normal BMI. The study also showed that the obese participants have twice the risk of hypertension compared to the participants with normal relative weight. [4]

Although obesity-related hypertension may be the result of a combination or overlap of a number of factors, activation of the sympathetic nervous system has been considered to have an important role in the pathogenesis of obesity-related hypertension. High-caloric intake can increase the level of norepinephrine (a chemical present in the body), which will narrow the blood vessel, thereby increasing the blood pressure on the arterial wall.  This leads to elevated sympathetic activity and hypertension.

According to researches, the possible mechanism for obesity-related hypertension is as follows:
  1. Renal mechanism: Visceral fat and metabolic abnormalities in obese person can increase the risk of chronic kidney diseases and structural damages. Damage to the nephrons (functional unit of the kidney) can cause sodium reabsorption and will interfere with the kidney function. Sodium reabsorption increases fluid retention and thus increases the blood volume. Increased blood volume, increases the pressure of blood in the blood vessel, thereby leading to hypertension.
  2. The renin-angiotensin system: The renin–angiotensin–aldosterone system regulates blood pressure and fluid balance in the body. Several studies have shown predominantly high levels of plasma renin, angiotensin, and aldosterone values in association with obesity. In obese individuals, adipose tissue elevates the production of angiotensinogen (component of the renin-angiotensin system), which cause blood vessels to become narrower leading to high blood pressure.

Management of obesity induced hypertension

Obesity-related hypertension is usually accompanied by:
  • Blood volume overload
  • High circulating plasma aldosterone
  • Insulin resistance
  • Stimulation of the sympathetic nervous system
  • Obstructive sleep apnea

Considering those conditions, the management of obesity induced hypertension should include lifestyle management measures and therapeutic interventions to lower blood pressure.

Various guidelines for the management of hypertension recommend that weight reduction or weight stabilization should be instituted in overweight patients. Researches shows that weight reduction have a beneficial effect on overall risk and in lowering blood pressure in obese patients. Medications combined with lifestyle modifications are required to reduce the risk of developing high blood pressure and improving quality of life.

  1. Lifestyle changes:
    • Eating a healthy diet with low sodium intake
    • Getting regular physical activity
    • Maintaining a healthy body weight and BMI
    • Limiting the amount of alcohol intake
    • Smoking cessation
  2. Medications (Antihypertensives):
    • Thiazide diuretics.
    • Angiotensin-converting enzyme (ACE) inhibitors.
    • Angiotensin-II receptor blockers (ARBs)
    • Calcium channel blockers.
    • Aldosterone antagonists
    • Beta blockers

Outlook

As the prevalence of obesity increases, the risk of hypertension and related cardiovascular disorders continues to increase. Hypertension is a key for numerous other diseases that can affect overall health and life expectancy. Weight reduction and maintenance of weight loss are important steps for prevention of hypertension. Anti-hypertension medications along with healthy lifestyle will reduce the amount of fat deposits in the body. Thus, it helps in managing hypertension in obese individuals.

References :

  1. Jiang SZ, Lu W, Zong XF, Ruan HY, Liu Y. Obesity and hypertension. Exp Ther Med. 2016;12(4):2395-2399.
  2. Hall JE, do Carmo JM, da Silva AA, Wang Z, Hall ME. Obesity-induced hypertension: interaction of neurohumoral and renal mechanisms. Circ Res. 2015;116(6):991-1006.
  3. Narkiewicz K. Obesity and hypertension—the issue is more complex than we thought, Nephrology Dialysis Transplantation. February 2006; 21 (2): 264–267.
  4. Aronow WS. Association of obesity with hypertension. Ann Transl Med. 2017;5(17):350.
  5. Hypertension and obesity: how weight-loss affects hypertension. https://www.obesityaction.org/community/articl-e-library/hypertension-and-obesity-how-weight-loss-affects-hypertension/ . Accessed on: 05-08-2020.
  6. Three Ways Obesity Contributes to Heart Disease. https://www.pennmedicine.org/updates/blogs/metabolic-and-bariatric-surgery-blog/2019/march/obesity-and-heart-disease. Accessed on: 05-08-2020.
  7. Kotsis, V., Stabouli, S., Papakatsika, S. et al. Mechanisms of obesity-induced hypertension. Hypertens Res 33, 386–393 (2010).
  8. How to treat hypertension in the obese. https://www.escardio.org/Journals/E-Journal-of-Cardiology-Practice/Volume-12/How-to-treat-hypertension-in-the-obese. Accessed on: 05-08-2020.
  9. Scholze J, Grimm E, Herrmann D, Unger T, Kintscher U. Optimal treatment of obesity-related hypertension: the Hypertension-Obesity-Sibutramine (HOS) study. Circulation. 2007;115(15):1991-1998.

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