The Relationship Between Obesity and Chronic Kidney Disease

Researchers estimate that there are about 850 million people around the globe living with chronic kidney disease (CKD). It’s also the world’s third fastest-growing cause of death.

Those numbers are scary. But we’re learning more and more every day about how to keep our kidneys healthy. Weight management is an important part of the equation — whether you have CKD or not. Nephrologist Hernán Rincón-Choles, MD, explains why.

Obesity and CKD risk

A BMI greater than 25 (having overweight) or 30 (having obesity) is a risk factor for kidney disease because it’s a primary driver of something called metabolic syndrome.

“Metabolic syndrome” (also called insulin resistance syndrome or dysmetabolic syndrome) is an umbrella term for a cluster of different health issues that raise your risk for heart disease and Type 2 diabetes.

You have metabolic syndrome if you have at least two of the following five characteristics, all of which are more common in people living with overweight and obesity:

• A large waist size, or having a lot of fat around the middle of your body
• A high level of a certain kind of fat, called triglycerides, in your blood
• A low HDL or “good” cholesterol level
• High blood pressure
• High blood sugar, even if you haven’t eaten

Research suggests that having metabolic syndrome makes you more likely to develop CKD.

“It’s important to note that even if your medication does a good job controlling your blood sugar, blood pressure or cholesterol levels, you’re still at an increased risk for kidney disease if you have overweight or obesity,” Dr. Rincón-Choles clarifies.

How weight impacts CKD

Not only do overweight and obesity raise your risk for CKD, but they’re also directly associated with disease progression.

Obesity and metabolic syndrome can inflame your glomeruli — the part of your kidneys that’s in charge of filtering your blood.

They can also cause hyperfiltration. That’s what happens when your damaged kidneys have to filter too much blood too fast. It’s normal for kidneys to experience hyperfiltration in certain short-term circumstances, like when you eat a protein-heavy meal. But chronic hyperfiltration causes kidney damage.

“If you already have CKD, metabolic syndrome increases the chances that your condition will progress to end-stage renal disease,” Dr. Rincón-Choles explains.

People with end-stage renal disease are treated with dialysis and, in some cases, a kidney transplant. Having obesity makes a transplant less likely because it increases your risk of complications, both in the immediate aftermath of the procedure and in the months and years that follow.

That’s the bad news. Here’s the good news: Losing weight might reverse metabolic syndrome and may slow disease progression in people already living with CKD.

Kidney-friendly weight loss advice

Getting to (and maintaining) a healthy body weight can reduce your risk of developing CKD or, if you already have it, slow the disease’s progression. But what a “healthy body weight” is — and the safest way to get there — varies from person to person.

Still, there’s some weight loss advice that makes sense for everyone.

Talk with your provider about losing weight

“If you have CKD or are high risk for developing it, it’s important that you don’t start a weight loss program without talking to your provider first,” Dr. Rincón-Choles stresses.

Losing too much weight or losing it too fast could harm your kidneys.

Avoid fad diets

They’re a bad idea across the board, but fad diets are extra dangerous if you have CKD.

“Many popular diets, like the keto diet and the carnivore diet, are high in protein and low in carbohydrates, which can be harmful,” Dr. Rincón-Choles explains.

A diet that’s too high in protein puts added strain on your kidneys. And when your body is burning fat rather than glucose from carbohydrates, you run the risk of going into ketosis, a metabolic state that can cause kidney damage.

Your doctor or a dietitian can help you develop a weight-loss plan that meets your nutritional needs and protects your health.

Keep an eye on how much fluid you drink

Researchers are working hard to better understand the role that hydration plays in kidney health. On the one hand, studies suggest that being well hydrated improves renal function and reduces your CKD risk. But once you have CKD, things can get more complicated.

A 2022 study describes the relationship between the amount of water a person with CKD drinks and their disease progression as “U-shaped.” In other words, both not drinking enough water and drinking too much water can speed up kidney damage.

Of course, most of us drink more than just water. So, it’s important to talk with your provider about everything you drink in a day. They can help you figure out what, if anything, about your routine could be affecting your renal function.

Use a food tracker

Keeping a food journal is a great way to make sure you’re providing your kidneys the nutrients they need. It can also help you notice and break eating patterns that accelerate CKD damage.

Dr. Rincón-Choles says it’s most important to track your intake of the following:

• Protein
• Carbohydrates
• Sodium
• Potassium
• Phosphorus

Bringing your food journal to appointments with your provider is a great way to get dietary advice that’s tailor-made for you.

Work out safely

Exercise is usually good for your kidneys — but there are enough exceptions to that rule that Dr. Rincón-Choles suggests reviewing your fitness routine with your provider.

“They can help you answer specific questions about how your condition affects the type, length and intensity of the workouts you can do safely,” he says.

Final thoughts

Weight loss and weight management can be challenging, especially if you’re living with chronic kidney disease. But you don’t have to go through the process alone.

“We’re here to help you learn about your condition,” Dr. Rincón-Choles encourages. “The more you understand about chronic kidney disease — and the more supported you feel — the more empowered you’ll be to make lifestyle changes. And those changes can make a big difference in your overall health.”