Obesity and Hypertension | What is the Link?
Excessive and abnormal fat accumulation in the body is defined as obesity. It is a result of an imbalance between the daily energy uptake and energy expenditure. It is caused by several modifiable and non-modifiable factors.
According to the World Health Organization, over 650 million adults are obese. Body Mass Index is one of the most common indices to classify obese and overweight individuals. It is calculated by taking a person's weight, in kilograms, divided by their height, in meters squared.
BMI = weight (in kg)/ height^2 (in m^2)
Individuals with a BMI equal to or greater than 25 are classified as overweight and those with a BMI equal to or greater than 30 are classified as obese.
Obesity has several adverse health outcomes such as increasing the risk of developing cardiovascular disorders, decreasing insulin sensitivity, type 2 diabetes, and promoting chronic inflammatory conditions.
Hypertension is defined as a persistent elevation of systemic arterial blood pressure. It is an important, modifiable risk factor for several disorders that cause significant morbidity and mortality worldwide.
Hypertension affects 1 in 4 adults globally and has significant effects on the physical, mental, and emotional health of the affected individuals, and greatly compromises their quality of life.
Obesity and Hypertension
Although hypertension can be due to several modifiable and non-modifiable risk factors, the role of obesity in causing hypertension is well established.
Consumption of a diet rich in fats, an abnormal level of carbohydrates can increase fat accumulation in the body, causing obesity and abdominal obesity.
Excessive dietary consumption increases the level of fat in the blood that deposits in blood vessels causing plaque formation and narrowing which in turn greatly compromises the blood supply of several organs and increases vascular resistance. Increased vascular resistance results in an increased workload on the heart which causes hypertension.
Inadequate renal perfusion results in the activation of the sympathetic nervous system (SNS) and the renin-angiotensin-aldosterone system (RAAS) which in turn causes a cascade that does more harm than good.
The RAAS increases sodium reabsorption, decreases sodium excretion, and changes renal vasculature all of which contribute to increased vascular resistance.
These mechanisms result in increased arterial pressures and can cause significant damage to the heart resulting in cardiovascular disorders, myocardial infarction, and death.
Link of Obesity with Hypertension
As reported by the Framingham Heart Study obese individuals accounted for 26% of cases of hypertension.
A prospective cohort study conducted for 14 years to monitor the incidence of hypertension. The highest risk of hypertension was found to be in individuals with an increased BMI.
Obese females had a 4.7 times higher incidence of hypertension when compared with those with a BMI under 23 kg/m2.
A detailed analysis of four prospective cohort studies covered 6328 individuals with a 23 year follow up. The results showed that overweight and obese children who grew up to obese adults had a risk of developing hypertension 2.7 times more than those with normal BMI, whereas losing weight decreased their risk of developing hypertension to levels similar to those individuals who were never obese. (8)
Just as obesity can increase the risk of hypertension, weight loss can decrease it. Weight loss can also decrease blood pressure as demonstrated by a meta-analysis of 18 studies that reported that dietary modifications that reduce weight by 3.5 kg decrease blood pressure by 4.0/1.1 mmHg.
Estimates indicate that for every 5 % increase in weight, the increased risk of developing hypertension is 20–30%.
Obesity can also cause treatment-resistant hypertension which results in the use of multiple medications to maintain optimal blood pressure.
How to Break the Link
The role of weight loss in decreasing obesity-related adverse outcomes is well supported by conclusive evidence.
Hypertension can be controlled by several medications but changes to lifestyle can reduce the risk of developing the disease, it can help maintain blood pressure, and prevent long-term sequelae.
Dietary modification such as the DASH diet, limiting alcohol consumption, and quitting smoking can help maintain the recommended BMI and optimize the effect of blood pressure control medications. Physical activity can help reduce weight and maintain normal blood pressure.
Bariatric surgery is now also considered an acceptable treatment for obesity-related hypertension. A retrospective review reported that hypertension was resolved in 45% of patients with hypertension before surgery.