Emerging research has found a link between obesity and kidney disease, with evidence stating that a high body mass index is one of the most significant risk factors for chronic kidney disease. Obesity increases the risk of developing diabetes and high blood pressure, leading to kidney disease. 

Similarly, a higher body mass index will force the kidneys to work harder to filter waste. This extra work increases the risk of obesity and kidney dysfunction long term. 

Kidney Function

The kidneys are two bean-shaped organs about the size of a large fist. They are located on either side of the spine below the ribs. The primary responsibility of the kidney is to filter blood and remove excess waste. 

Blood will pass through the kidneys about 40 times throughout the day. In doing so, the blood is "cleaned" of any waste while the salt, water, and mineral levels are adjusted as needed for proper bodily function. The cleaned blood will reenter the bloodstream while the waste is turned into urine. 

The Link Between Obesity and Kidney Disease

When a patient is overweight, their kidneys must work harder to filter the waste. This "hyperfiltration" needs to occur to meet the "heightened metabolic demands of the increased body weight." Over time this increased pressure on the kidneys can cause long-term damage and raise the risk of chronic kidney disease. 

In addition, obesity and kidney disease are also correlated due to the prevalence of diabetes and hypertension in overweight individuals. According to the CDC, diabetes and hypertension are the leading causes of kidney failure. Diabetes contributes to kidney disease as high blood sugar levels can damage the blood vessels in the kidneys. Hypertension can cause kidney damage due to narrowing arteries around the kidneys, restricting blood flow. 

Obesity and Diabetes

Kidney disease caused by diabetes is known as diabetic kidney disease or diabetic nephropathy and is the number one cause of kidney failure. Diabetes is a disease characterized by high blood sugar (glucose) levels. In healthy individuals, blood glucose levels are controlled by the secretion of insulin from the pancreas. However, in people with type 2 diabetes, cells don't respond correctly to insulin. This results in blood sugar being unable to enter cells and be stored for energy, causing high blood sugar.

High blood sugar levels can damage the blood vessels around the kidneys. If left untreated, this can also lead to high blood pressure (hypertension). 

Obesity and Hypertension

A 5% increase in weight can lead to a 30% increase in the risk of hypertension, affirming the link between obesity and kidney failure. Studies have concluded that hypertension is the second leading cause of kidney failure. 

The kidneys rely on your blood vessels, and when those blood vessels become damaged, there is an increased risk of kidney dysfunction. Prolonged high blood pressure can cause the arteries around the kidneys to narrow or harden. When the arteries are impaired, they won't be able to properly filter and clean the blood, regulate fluids, or adjust hormone levels in the body. 

As a result, the kidneys can stop functioning and ultimately fail, which could lead to end-stage renal disease. 

How to Manage Obesity and Kidney Disease 

The good news is that patients who can manage their obesity significantly reduce their risk of kidney failure and end-stage renal disease. Weight loss will drastically decrease the effects of diabetes and high blood pressure, if not reverse these conditions, which can prevent kidney disease. For patients with extreme obesity, bariatric surgery may be the best option for their health. We encourage patients to understand the risks associated with obesity and kidney disease and the impact if may have on their health.