Stage 4 Kidney Disease and Weight Loss: Uncover the Hidden Causes, Risks, and Effective Management Strategies

Chronic Kidney Disease (CKD) is a global health concern affecting millions. It's characterized by the gradual damage to the kidneys over time, leading to a decline in their ability to filter waste from the blood. This can result in serious health complications like anemia, nerve damage, and high blood pressure. While weight management is often recommended for individuals with CKD, both intentional and unintentional weight loss can present unique challenges. This article explores the complex relationship between stage 4 kidney disease and weight loss, examining the causes, risks, and strategies for safe and effective management.

Understanding Chronic Kidney Disease

Your kidneys are two bean-shaped organs on either side of your spine, just below the rib cage. They’re only about the size of a fist, but they’re responsible for filtering all the blood within your body. In fact, a healthy kidney can filter about a half cup of blood every single minute. They remove waste products and extra water to help your body maintain homeostasis and function properly. Chronic kidney disease happens when an underlying condition gradually damages the kidneys over time.

Unfortunately, CKD often doesn’t present any symptoms until it’s advanced to later stages, which makes it an increasingly dangerous condition. Stage 4 CKD is characterized by a severely decreased kidney function, with an estimated glomerular filtration rate (eGFR) between 15 and 29. At this stage, the kidneys are moderately to severely damaged and are not properly filtering waste from your blood. You may also have protein in your urine. Protein waste, toxins and minerals build up in the body and lead to uremia with symptoms such as nausea, vomiting, loss of appetite, abnormal taste, bad breath, nerve and sleep problems, difficulty concentrating and fatigue. Stage 4 CKD is the last stage before kidney failure.

The Association Between Kidney Disease and Body Weight

It’s common for people with chronic kidney disease (CKD) to be either overweight or underweight. Many causes of chronic kidney disease are correlated to obesity and being overweight. If you have gained weight, your doctor may suggest weight loss. However, in certain situations, kidney disease can unintentionally lead to weight loss. IgA nephropathy (IgAN) can also cause you to gain weight from fluid retention and lose fat in certain areas of the body due to kidney-related issues. You’ll need to monitor these changes with your health care team.

Obesity may increase the risk of developing CKD as well as its progression to advanced stages. As many as 1 in 3 cases of kidney disease in the United States are associated with obesity. Additionally, obesity is associated with the development of several risk factors for kidney disease, such as: Type 2 diabetes, Hypertension (high blood pressure), Hyperlipidemia (high cholesterol), Coronary heart disease and Sleep disorders. Diabetes and high blood pressure are the main causes of kidney disease. These two conditions are responsible for up to two-thirds of all cases of CKD. Some research shows weight gain may account for up to 75 percent of the risk of high blood pressure. Having a BMI of 30 or higher is associated with diabetes. In addition to increasing your risk of developing kidney disease, people with higher body weights and CKD may progress to kidney failure more quickly than people who have healthy BMI scores. In those with a rare type of kidney disease called immunoglobulin A nephropathy, complications such as high blood pressure, proteinuria (protein in the urine), and kidney lesions were more common in those with higher body weights.

Benefits of Weight Loss in CKD

Therefore, losing weight can have several positive impacts on kidney disease. Being obese or overweight can put a lot of strain on your kidneys, directly increasing overall blood pressure. Over time, elevated blood pressure will strain the arteries around the kidneys, causing them to weaken, narrow, or completely harden. This means there are fewer arteries delivering blood to the kidneys, which leads to filtration problems and extremely high levels of strain.

Another benefit of weight loss with kidney disease is the ability to control blood glucose levels more naturally. As you lose weight, your body’s insulin resistance may improve. While this is especially important for individuals living with diabetes, it can also reduce the strain on your kidneys and decrease your risk of developing prediabetes or type 2 diabetes. Since losing weight can improve overall kidney function, it can also reduce levels of proteinuria. Proteinuria occurs when there are high levels of protein present in your urine. This is an indication that they’re not filtering waste products efficiently, which can cause several complications over time.

The Risks of Rapid Weight Loss in CKD

While weight loss can help reduce your risk of chronic kidney disease and decrease its progression, rapid weight loss can be dangerous. According to a recent study, individuals who lose weight quickly with chronic kidney disease tend to have a disproportionately higher loss of lean body mass than loss of fat mass. Unfortunately, fat loss is the best way to decrease blood pressure, so rapid weight loss tends to have adverse effects. In fact, there are several risks associated with rapid weight loss and chronic kidney disease.

Muscle Loss: Rapid weight loss can result in lean muscle mass loss rather than fat loss.
Electrolyte Imbalances: Losing weight too quickly can also cause an electrolyte imbalance throughout the body.
Nutrient Deficiencies: Reducing caloric intake by too much can result in nutrient deficiencies.
Kidney Failure: When you combine all of these factors, you can end up experiencing kidney failure.

Dietary Restrictions and Weight Loss Challenges

If you’re living with kidney disease, you may have to follow a special diet to help balance the levels of electrolytes, minerals, and fluid in your body. Your diet may limit some of the lower-calorie food options that will keep you feeling full while trying to lose weight.

Examples of foods that may need to be limited if you have kidney disease include:

Read also: Nutrition and stage 2 CKD

High-sodium foods - Added table salt, packaged foods, and fast food
Protein - Meat, beans, and nuts
High-phosphorus foods - Deli meat, dairy products, oatmeal, beans, and soft drinks
High-potassium foods - Oranges, bananas, potatoes, dairy products, and whole wheat bread

A high-protein diet has been proposed as a way to increase weight loss while still feeling full. However, if you’re following a low-protein diet to treat kidney disease, you may not be able to eat high-protein foods. If you’re following a low-phosphorus or low-potassium diet, talk to your doctor and dietitian about which kidney-friendly foods you can add to your grocery list. Some examples of low-potassium vegetables include iceberg lettuce, cabbage, cucumbers, onions, and bell peppers. Low-potassium fruits include apples, berries, and pears.

Unintentional Weight Loss as a Symptom of Kidney Disease

Although higher body weight is related to kidney disease, it’s also true that kidney disease can cause some people to lose weight. As cited in Current Opinion in Nephrology and Hypertension, you may have an increased risk of dying if you lose weight or body fat when you have kidney disease. Kidney disease can cause you to lose weight if you don’t eat enough calories. As mentioned, a BMI of less than 18.5 is considered underweight.

If you have kidney failure, you may experience symptoms like nausea, vomiting, and loss of appetite that make it hard for you to eat enough food. If you’re on dialysis, your body may need more calories than you’re used to. Additionally, if you have a restricted diet, you may have to avoid some foods you enjoy eating. If you don’t get enough calories every day, you may start to gradually lose weight. Some people with kidney failure can also develop wasting syndrome (called cachexia), which can cause the loss of fat and muscle. Wasting syndrome is caused by more than just a loss of appetite. In people with end-stage renal disease (ESRD), wasting syndrome can be caused by inflammation and differences in metabolism. Additionally, some appetite-suppressing hormones may build up in your body if your kidneys can’t effectively filter them out of your blood.

One of the unusual things that can happen in people living with the kidney disease called complement 3 glomerulopathy (C3G) is that some parts of the body might become unusually thin. This thinness can be in specific areas, like the muscles or fat tissue in certain parts of the body. Complement 3 is one of several proteins that team up in the body’s defense system, known as the complement system, to fight off infections. In C3G, the complement system can sometimes destroy fat cells under the skin, but it does this unevenly throughout the body. This process leads to some parts of the body appearing abnormally thin and others abnormally large. If you notice that you’re losing weight without trying, talk to your doctor right away. Your doctor or dietitian may be able to help you find ways to increase your daily calories.

Strategies for Safe Weight Loss in Stage 4 CKD

While losing weight is still crucial with CKD, there are important safety measures to take.

Focus on Nutrient-Dense Foods: Choosing whole, nutrient-dense foods is crucial when you have chronic kidney disease, and it can help with safe, gradual weight loss. Focus on incorporating fresh fruits, vegetables, lean proteins, healthy fats, and whole grains into your diet. These foods provide essential vitamins, minerals, and fiber while minimizing the intake of processed ingredients, additives, and excessive sodium. Avoid high-potassium and high-phosphorus foods like bananas, oranges, and dairy products if your doctor or dietitian recommends it.
Monitor Protein Intake: Protein is essential for your overall health and can help you maintain muscle mass during your weight loss journey. However, excessive protein consumption can put a lot of strain on your kidneys and result in proteinuria. Talk to your doctor or a registered dietician to better understand how much protein you should consume daily. The Kidney Disease Outcome Quality Initiatives (K/DOQI) Nutrition Guidelines suggest that a protein intake of 0.6 grams per kg of body weight may be beneficial when glomerular filtration rate (GFR) drops below 25, or approximately 25 percent remaining kidney function. This lower-protein diet is thought to have a protective effect on the kidneys. However, it also brings the risk of protein malnutrition, with muscle wasting and low albumin levels.
Gradual Calorie Reduction: Weight loss happens when you’re in a caloric deficit, but that doesn’t mean you should starve yourself. Therefore, gradual calorie reduction is the best way to lose weight safely with CKD. Try to create a deficit of about 500 to 1,000 calories daily, which typically equates to losing about one to two pounds per week. However, talk to your doctor or a registered dietician first to ensure this is a safe deficit goal for your needs. When you make changes in your diet, your calorie intake may decrease, resulting in undesirable weight loss. Decreasing your protein intake alone can result in 200 to 400 fewer calories a day. Weigh yourself and track your weight weekly to see if you need more calories.
Read Nutrition Labels Carefully: Different ingredients have different effects on your body. For example, highly processed foods can be difficult to digest and have little nutritional value. This makes them empty calories. To make sure you’re getting the nutrients your body needs to function, always take the time to read nutrition labels thoroughly. Additionally, limit your sodium, potassium, and phosphorus intake during your weight loss journey, as these minerals can put more stress on your kidneys. As kidney function decreases, phosphorus isn’t removed from your body efficiently and can build up in the blood. At the same time, calcium is not absorbed well from your food, leading to low blood levels. In response, parathyroid hormone (PTH) production increase and causes a release of calcium and phosphorus from your bones. The loss of calcium and phosphorus from your bones causes bones to weaken and the increase of phosphorus and calcium in your body can cause calcifications in your heart, blood vessels and other soft tissues within your body. Check food ingredient lists for any type of phosphorus additive (phosphoric acid, hexametaphosphate, triphosphate, etc.). If kidneys aren’t able to remove enough potassium to maintain normal blood levels in stage 4 CKD, you will need to limit high-potassium foods. Your doctor may prescribe a potassium restriction of 2,000 to 3,000 mg a day. Most kidney diets start with a goal of 1,500 to 2,000 mg per day or the amount recommended by your doctor or dietitian. The sodium recommendation for stage 4 CKD is 1,000-4,000 mg/day based on fluid balance, blood pressure and other diseases that may affect sodium requirements.
Incorporate Regular Exercise: Getting plenty of exercise is one of the best things you can do to safely lose weight with chronic kidney disease. Exercise also has tremendous benefits on your cardiovascular health, which can support the healthy functioning of the kidneys. Try to aim for at least 150 minutes of moderate-intensity aerobic exercise per week.
Consult with Your Doctor and a Registered Dietitian: You should never start a new diet or exercise regimen without consulting with your doctor-especially if you have chronic kidney disease or any other underlying condition. Your doctor will be able to assess your health status, stage of chronic kidney disease, and individual dietary needs to help support healthy kidney functioning.

Managing Stage 4 CKD and Preparing for Potential Kidney Failure

At this stage, you will need to see a nephrologist (kidney doctor). Your nephrologist will treat Stage 4 CKD with medicines that help with your symptoms and other health problems that kidney disease can cause, such as diabetes and high blood pressure.

These medicines include:

Blood pressure medicines like ACE inhibitors and ARBs (even if you do not have high blood pressure, these medicines can slow the damage to your kidneys to keep them working well as long as possible)
Diabetes medicines to keep your blood sugar at a healthy level (even if you do not have diabetes)
Calcium and vitamin D supplements to keep your bones strong
Diuretics to help with swelling (these are medicines that help your kidneys get rid of salt and water and make you urinate more)
Erythropoiesis-stimulating agents (ESAs) or iron supplements to help with anemia (not enough red blood cells in your body)
SGLT2 inhibitors to protect your kidneys and lower blood sugar levels
Nonsteroidal mineralocorticoid receptor antagonists (nMRA) to reduce swelling and help prevent further kidney damage

Your doctor may tell you to stop taking medicines that can damage your kidneys, such as pain medicines called NSAIDs (nonsteroidal anti-inflammatory medicines). Your nephrologist will decide if your kidneys are close to failure and if you need to start treatment. If you need treatment, they will talk with you about your choices, which include: Dialysis: a treatment to clean your blood when your kidneys cannot. A kidney transplant: surgery to give you a kidney from someone else's body. You may be eligible to get on the transplant waitlist when your eGFR is 20 or below, but it's a good idea to start thinking about the process when your GFR is between 25 and 30. Starting the conversation early - even before you reach end-stage kidney failure - gives you time to explore your transplant options and prepare. Understand the transplant process. There is usually no cure for CKD, and you usually cannot reverse the kidney damage you already have by the time you get to stage 4 CKD. However, you can take steps to slow down the damage to your kidneys and help you feel your best.

To slow down the damage to your kidneys, your doctor will recommend that you:

Have visits with a nephrologist about every three months.
Meet with a dietitian (nutrition expert) to help you create and follow a kidney-friendly eating plan.
Keep your blood pressure at a healthy level. Your doctor may prescribe blood pressure medicines like ACE inhibitors and ARBs.
Keep your blood sugar at a healthy level if you have diabetes.
Be active for at least 30 minutes on most days of the week. This can be anything from walking or riding a bike to swimming or dancing.
Quit smoking or using tobacco.

The Role of Weight Change in CKD Progression and Mortality

Excess body weight is a risk factor for the progression of chronic kidney disease (CKD), but weight loss in CKD has been associated with higher mortality. Consequently, blanket weight loss recommendations in this population are controversial. Little data is available on the patterns of weight‐change in CKD. Loss to follow‐up with the renal unit did not necessarily preclude a collection of mortality data; therefore, no more than 54 patients (17%) had uncertain mortality status at the end of the study. As at 30 September 2022, 128 patients (41.3%) had died, of whom 11 died after being otherwise lost to follow‐up. Mortality was similar across the different baseline CKD stages. BMI at baseline did not predict subsequent death but age, ≥5% weight loss and ≥5% weight gain at 12 months were associated with a higher risk of subsequent death.

Patients with moderate/severe CKD experience significant weight‐change, but this has no relationship to baseline kidney function. Clinically significant weight change is common in moderate to severe chronic kidney disease but has no relationship to baseline kidney function. A significant proportion experienced clinically significant weight changes, but because these changes were balanced, the mean weight for the group fell only modestly during follow‐up. There was no association between baseline severity of CKD and subsequent weight change. The authors found a U‐shaped association between clinically significant weight change during the first year and death or the renal endpoint. This emphasizes the risk of confounding in relying on observational studies to guide weight loss/gain advice to patients with moderate to severe CKD and overweight or obesity. Until results from randomized, controlled, intervention studies targeting the weight change in the CKD population are available, clinicians must rely on clinical judgment to guide weight change advice in this population.

Understanding Wasting/Cachexia in CKD

Wasting/cachexia is prevalent among patients with chronic kidney disease (CKD). Eighteen to 75% of adults with end-stage renal disease (ESRD) undergoing maintenance dialysis showed some evidence of wasting. The differences in prevalence of wasting may be due to the different ESRD patient population mix reported, in the context of race, age, and prevalence of comorbid conditions such as congestive heart failure, diabetes mellitus, and liver disease. Wasting, defined by the World Health Organization as low weight for height, was thought to be the direct consequence of inadequate nutrition intake or malnutrition. As a result, the terms, “wasting”, “cachexia”, and “malnutrition” were used interchangeably. Although inadequate nutrition may contribute to wasting or cachexia, other factors including systemic inflammation, perturbations of appetite-controlling hormones from reduced renal clearance, aberrant neuropeptide signaling, insulin and insulin-like growth factor resistance, and metabolic acidosis, may be important in the pathogenesis of CKD-associated wasting. The wasting/cachexia syndrome in CKD patients consists of anorexia, increased energy expenditure, decreased protein stores characterized by a low serum albumin, and loss of body weight and loss of muscle mass. Importantly, the individual components of this syndrome all represent risk factors for mortality in patients with CKD, which is 100-200 times higher than the general population.

The wasting/cachexia syndrome should be distinguished from malnutrition, which is defined as the consequence of insufficient food or an improper diet. Hunger, which is an adaptive response, characterizes malnutrition whereas anorexia is prevalent in patients with wasting/cachexia. Energy expenditure decreases as a protective mechanism in malnutrition whereas it remains inappropriately high in cachexia/wasting. In malnutrition, such as in simple starvation, fat tissues are preferentially lost and lean body mass (LBM) and muscle mass is preserved until the advanced stages, whereas in cachexia/wasting, muscle is wasted and fat is relatively underutilized. Restoring adequate food intake or altering the composition of the diet reverses malnutrition.

Cachexia was recently defined as “a complex metabolic syndrome associated with underlying illness and characterized by loss of muscle, with or without loss of fat” by a group of scientists and clinicians participating in a consensus conference on cachexia. In the context of CKD, the term protein-energy wasting (PEW) has been proposed by The International Society of Renal Nutrition and Metabolism (ISRNM) to describe a “state of decreased body stores of protein and energy fuels (body protein and fat masses)”. The ISRNM suggested that the term cachexia be reserved for only the most severe forms of PEW. However, there is no obvious distinction between PEW and cachexia from a pathophysiology standpoint. Limiting the term cachexia to the extreme forms of PEW could be considered too restrictive.

Diagnostic Criteria for Cachexia/PEW in CKD

The diagnostic criteria for cachexia (proposed by the SCWD) and for PEW (proposed by the ISRNM) are similar, but not identical. Weight loss of at least 5% over 12 months or fewer, or a BMI < 20 kg/m2, is necessary for the diagnosis of cachexia; three of the following five additional criteria are also required: decreased muscle strength, fatigue, anorexia, low fat-free muscle mass, and abnormal biochemistry (including elevated inflammatory markers such as C-reactive protein (CRP) or interleukin (IL)-6, anemia [Hb < 12 g/dL] and hypoalbuminemia. The proposed criteria for a diagnosis of PEW fall into four distinct categories: (1) biochemical indicators, (2) low body weight, reduced body fat or weight loss, (3) decreased muscle mass, and (4) low protein or energy intake.

Evidence of low body weight, reduced body fat or weight loss are important indicators of cachexia/PEW. Body mass index (BMI) is proposed as a method of assessing appropriateness of body weight. Although BMI gives little information about body composition, BMI is a useful means of assessing PEW. BMI is strongly correlated with LBM at the low end of the BMI spectrum, and low BMI is a consistent predictor of mortality in both adults and children on maintenance dialysis. However, BMI is not a very precise parameter of nutritional status in patients in whom gross imbalances in fluid homeostasis are commonly observed, such as in patients with ESRD, CHF, and liver disease. Furthermore, in patients with significant muscle wasting with relatively well-preserved fat mass, small changes in BMI may well be obscured by imbalances in fluid homeostasis. In this respect, some investigators have preferred to use subjective global assessment (SGA) as a surrogate marker in assessing the nutritional status of patients with ESRD.

Unintentional weight loss or reduction in weight of 5% or more over 3 months, or 10% or more over 6 months are suggested as indicators of cachexia/PEW, independent of absolute BMI. Linear growth failure in children with CKD was highlighted as central to the diagnosis of cachexia, and has been associated with a greater mortality risk in children on maintenance dialysis. However, the etiology of growth retardation in CKD is multifactorial, including other factors such as delayed sexual maturation, bone disease, acidosis, and growth hormone/insulin growth factor resistance. Reduced muscle mass appears to be the most valid criterion for the presence of PEW in CKD, and is also emphasized in the diagnostic criteria for cachexia. Mid-arm circumference has been shown to correlate with quality of life and survival in adult patients on maintenance hemodialysis (HD). Anorexia is one of the suggested criteria for cachexia, while low protein and/or energy intake is a criterion for PEW. Both subjectively reported anorexia as well as measured low protein or energy intake has been associated with increased mortality in adult ESRD patients.

Among biochemical indicators of PEW, low serum albumin stands out as a consistent predictor of mortality in epidemiological studies of both adult and pediatric ESRD patients. A low serum albumin concentration is by far the strongest predictor of mortality and poor outcomes in adult ESRD patients on maintenance dialysis when compared to any other risk factors, including traditional risk factors (hypertension, smoking, hypercholesterolemia, diabetes, and obesity) and non-conventional ones (anemia measures, oxidative stress, minerals and bone surrogates, dialysis treatment and technique). Approximately two thirds of all maintenance dialysis patients in the USA exhibit “relative hypoalbuminemia”, i.e., a serum albumin <4.0 g/dL, as suggested by the National Kidney Foundation Kidney Disease Quality Outcome Initiative for the diagnosis of PEW. Relatively low serum prealbumin (e.g., <30 mg/dL) is another indicator of PEW and a strong predictor of outcomes in maintenance dialysis patients. Low serum cholesterol has also been proposed as a biochemical indicator of PEW.

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