Overweight and Obesity

Obesity Risk factors Prevention, daily life, and wellbeing

Last Updated: October 01, 2024

Medically reviewed by NKF Patient Education Team

Overweight and obesity put stress on the kidneys and worsen health. Managing weight can help protect kidney function and your overall health.

Table of Contents

About Overweight and Obesity

Overweight and obesity are chronic (long-term) health conditions where you have a larger body size and more fat cells than what is considered healthy. Everyone needs some body fat for energy, heat insulation, and other body functions. Yet, having too much can lead to serious health problems. 

Overweight and obesity are risk factors for other conditions that can harm your kidneys, like type 2 diabetes, high blood pressure, and heart disease. These are some of the most common risk factors for chronic kidney disease (CKD). 

Obesity can also directly increase your risk of CKD by:

  • Causing inflammation (swelling) in the glomeruli (tiny filters) inside your kidneys, and/or
  • Increasing stress on the filters in your kidneys by making them work harder than usual to filter your blood (also known as “hyperfiltration”). Over time, this can lead to scarring and breakdown of the filters.

For people living with kidney failure, obesity can be a barrier to getting a kidney transplant. This is because people with obesity have a high risk for complications during the surgery and in the months and years after transplant.

Almost 70% of adults in the United States have either overweight or obesity. Obesity also affects about 20% of children and teens.

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Signs and Symptoms

Body Mass Index (BMI)

The main sign of overweight and obesity is your body mass index (BMI). BMI compares how much you weigh to how tall you are. It is important to know that BMI is a general screening tool to measure body size and does not directly measure body fat or show where in the body that fat is concentrated. As a result, some people with muscular builds, such as athletes, may have a BMI that falls into the overweight range even though they may not have excess body fat. 

For adults 20 years old and older: Your BMI can be calculated by entering your height and weight into the calculator below.

Compare your number to the BMI categories below:

Underweight

This category includes people with a BMI under 18.5. Like having too much weight, not having enough weight also comes with extra health risks. These can include weak bones, anemia (low levels of red blood cells), feeling tired (not enough energy), frequent infections, and problems with your skin, hair, or teeth. Newer research also suggests that a BMI under 18.5 may increase the risk of kidney failure.

Healthy weight

This category includes people with a BMI between 18.5 and 24.9. Having a BMI in this range suggests you are likely at a healthy weight.

Overweight

This category includes people with a BMI between 25 and 29.9. Having a BMI in this range may not increase your risk of kidney disease, but it does increase your risk for other weight-related health problems such as type 2 diabetes, high blood pressure, and heart disease.

Obesity

This category includes people with a BMI of 30 or more. Having a BMI in this range increases your risk of kidney disease and other weight-related health problems. This category is further divided into 3 subcategories:

  • Class 1 Obesity: BMI of 30 to 34.9
  • Class 2 Obesity: BMI of 35 to 39.9
  • Class 3 Obesity: BMI of 40 or higher

As BMI goes up, the risk of weight-related health problems goes up too. So, these subcategories are used to help further categorize your risk of weight-related health problems. For example, somebody with a BMI of 45 (class 3 obesity) has a different level of risk than somebody who has a BMI of 32 (class 1 obesity). 

For children and teens between the ages of 2 and 19: BMI is calculated by comparing the child’s BMI to growth charts for children who are the same age and sex. The results are reported as a “percentile”, which is a way to show where someone stands compared to others. A higher number means the child’s BMI is higher than other children who are the same age and sex. The calculator below can help you determine the BMI for your child or teen.

  • Underweight: BMI below the 5th percentile 
  • Healthy weight: BMI between 5th and 85th percentile
  • Overweight: BMI between 85th and 95th percentile
  • Obesity: BMI in or above the 95th percentile

Waist Circumference (WC)

Another sign of overweight and obesity is your waist circumference. Where the extra fat is in your body matters when thinking about its impact on your health, even if your BMI is in the healthy weight range. For example, a higher amount of body fat around your waist causes more health problems than if that fat were found around your hips instead. 

Measuring your waist circumference is easy if you have a tape measure. Put the end of the tape measure at the top of your hip bone, then bring it all the way around your body (level with your belly button). Make sure the tape measure is not too tight and that it’s straight all the way around. Take a normal breath and check the number on the tape measure right after you breathe out. Do not hold your breath or pull your belly in while measuring. Consider asking someone to help if you’re having trouble measuring by yourself. In the United States, the following waist circumference results are associated with a higher risk for weight-related health problems:

  • Men: 40 inches or higher
  • Women: 35 inches or higher

Everybody has a different body size and carries body fat in different ways. So, your BMI and waist circumference must be interpreted within the context of your specific situation. Talk to your healthcare professional about your weight and the impact on your metabolic health.

Causes

Overweight and obesity are complex health issues resulting from a combination of factors. Some of the most common factors leading to obesity include the following:

Lifestyle habits and behaviors

Your body turns all the calories you consume (eat and drink) into energy. This energy is either used quickly or stored for later use in fat cells. When your body gets more calories (energy) than it needs, your fat cells can grow faster than your body is able to burn it off. Also, your quality of nutrition, level of physical activity, stress levels, use of alcohol and/or recreational drugs, and amount of good-quality sleep every night can all affect your risk of overweight and obesity too. Studies have shown more frequent snacking and alcohol intake while doing less physical activity during the COVID-19 pandemic has contributed to more people developing obesity.

Environment

Where you live, work, and/or go to school have a very big impact on your risk of overweight or obesity. This includes things like whether you have safe and convenient places to walk or exercise, the types of restaurants and food stores available nearby, and even having safe air to breathe and clean water to drink. Your environment also includes the lifestyle habits and cultural norms of your family and friends – these can directly impact your habits too. This is especially true for children who are forming habits based on what they see their parents do. 

Finances

Your financial situation also affects your risk for overweight or obesity. The amount of money you can spend on food will influence the types of foods you can afford. People who do not have reliable access to healthy foods (also known as “food insecurity”) have a very high risk of overweight or obesity. Your finances can also affect how and when you can be physically active, your level of stress, and many other lifestyle habits.

Family history and genes

Some people are naturally at a higher risk of having a larger body size. Newer research suggests genes may play a role. A gene is a small piece of DNA, or a basic unit of heredity. DNA carries genetic information, or instructions, for all living things. Some examples of how genes can lead to obesity include increasing feelings of hunger or cravings, decreasing your ability to feel full after a meal, or slowing your metabolism (how your body converts food into energy). Even if you are at high risk for obesity because of your genes, you can still decrease your risk through healthy lifestyle habits.

Certain health conditions and medications

Some health conditions can increase your risk of weight gain and lead to overweight or obesity. Examples include polycystic ovary syndrome (PCOS), Cushing syndrome, depression, or underactive (low) thyroid. These conditions need to be treated before any weight gain can be stopped and potentially reversed. A serious injury or permanent disability that limits your ability to do physical activity can also increase your risk of weight gain. 

 

Some medications can also lead to weight gain. The most common examples include medicines used for depression, schizophrenia or other behavioral health conditions, seizures, diabetes, high blood pressure, heart disease, birth control, and to prevent rejection for kidney transplants. Always talk to your healthcare professional if you notice weight gain while taking medication. If it is related to the medicine, there may be a possibility to switch to something else that might not have the same side effect (though not always possible).

Some of these factors cannot be changed, like your family history or genes. But taking steps to make healthier habits and work towards a healthy weight can help lower your risk of overweight or obesity and weight-related complications. 

Complications

Overweight and obesity can increase your risk for other health problems, including:

Diagnosis

As noted above, a diagnosis of overweight or obesity is largely informed by your BMI. But remember - that number alone doesn’t tell your full story! Your health care professional will also use information from your medical history, physical exam, and/or laboratory tests to inform the diagnosis and assess your risk for complications. 

Treatment

Overview

Treatment for overweight and obesity often requires a combination of strategies to be successful. The following list includes the most common options proven to be effective. Healthy nutrition (eating habits) and physical activity are essential and cannot be ignored. Still, most people are not able to lose enough weight with healthy eating and physical activity alone. So, weight-loss medication and/or surgery can be helpful tools to use in combination with healthy eating and physical activity. 

Healthy and long-lasting weight loss takes time, usually at a rate of 1-2 pounds per week. Also, the treatment goal is not a “perfect weight”. Studies have shown that losing just 5-10% of your body weight can go a long way in reducing your risk of weight-related health problems like diabetes, high blood pressure, and high cholesterol. As an example, somebody who weighs 250 pounds may be able to lower their health risk by losing just 12-25 pounds.

Treating overweight and obesity is about much more than your number on the scale or BMI. The goal is to increase your overall health and lower your risk for complications. Believe it or not, there are unhealthy ways to lose weight. Focusing only on weight loss (instead of also making sure you do it in a healthy way) can lead to more health problems.

Nutrition

A healthy approach to eating is the cornerstone of treating overweight and obesity. The first place to start is often looking at how many calories you consume each day - this includes everything you eat and drink. Everybody has different calorie needs based on their sex, age, and physical activity level. Work with your healthcare professional or dietitian to see how many calories are recommended for you based on the needs of your metabolism. 

Another step is to evaluate the types of calories and ingredients you are eating. Limiting your intake of saturated fat, sodium, added sugars (especially soda pop, sports drinks, energy drinks), and alcohol can be very helpful for losing weight. Read the Nutrition Facts label to see how healthy or unhealthy something may be for you. 

It is important to combine the two steps above to keep your body healthy. Just focusing on limiting your calories likely will not help improve your overall health if the calories you are eating do not have enough healthy nutrients, like fiber, lean proteins, plant-based proteins, vitamins, and healthy oils. It may sound strange, but it is possible to have obesity and malnutrition (or malnourishment) at the same time – when your body does not have the right nutrition to maintain its regular function.

Many patients have lots of questions about eating healthy while also living with chronic kidney disease, especially people with stage 4 CKD, stage 5 CKD (not on dialysis), or on hemodialysis or peritoneal dialysis. So, be sure to work with a kidney dietitian to build a healthy eating plan that works for you. The NKF Nutrition Coach also has many helpful resources.

Exercise

Physical activity is another important part of treating overweight and obesity. Getting at least 150 minutes of moderate intensity exercise each week has been shown to improve your health and lower your risk for many chronic diseases and complications. “Moderate intensity” means you should be able to say a few words in a row but not sing during exercise. Don’t feel like you must do it all at once either! Spreading it out throughout the week is better than fitting it all in one or two days. 

Most adults are recommended to also do muscle-strengthening activities for major muscle groups on 2 or more days each week. These activities can give additional health benefits. 

Depending on your health situation, it may be best to talk with your healthcare professional before starting an exercise regimen. This is especially true if you have a history of heart disease or kidney failure.

Quality Sleep

Research has shown that not getting enough quality sleep can lead to a high BMI. Regularly getting less than 7 hours of sleep per night can affect the hormones (natural chemical messengers or signals) that control hunger urges. In other words, not getting enough quality sleep can make you more likely to overeat or not recognize your body’s signals telling you when you are full. Try to get enough sleep so you are well-rested.

Reduce Stress

High levels of stress over a long period of time can increase your risk of overweight and obesity. Stress affects the brain, telling your body to make hormones (natural chemical messengers or signals) like cortisol. Cortisol increases your hunger urges, telling you to eat more, and helping your body to store extra fat. Finding ways to reduce and manage stress in your life can help you lose weight and/or prevent weight gain.

Medications

Medications can help people with obesity achieve their weight loss goals when used in combination with healthy nutrition and physical activity. Weight-loss medicines are generally approved by the US Food & Drug Administration for adults with a BMI of 30 or more, or a BMI of 27 or more and one or more weight-related health condition. Some (but not all) weight-loss medicines are also approved to treat obesity in children 12 years of age or older.

Medications for weight-loss in people with overweight or obesity include:

  • GLP-1 receptor agonists, like liraglutide (Saxenda), semaglutide (Wegovy), or tirzepatide (Zepbound). These medicines help slow digestion and increase your feelings of fullness after meals.
  • Fat absorption inhibitors, like orlistat (Alli or Xenical). This medicine helps block some of the fat in the foods you eat from being absorbed from the intestines.
  • Appetite reducers, like naltrexone/bupropion (Contrave) or phentermine/topiramate (Qsymia). These medicines help lower the craving signals coming from your brain.

Each medication option comes with different risks and benefits. Some may be better options than others based on your other health conditions (including kidney disease). Talk with your healthcare professional about the different options available to see which might be better for you. 

Weight Loss Surgery

Weight loss surgery (also known as bariatric or metabolic surgery) is another effective tool to help people with obesity lose weight and lower their risks of weight-related health problems. There are many different types of procedures available. These surgeries are grouped together by how they work:

  • Restrictive surgery – reduces the size of your stomach
  • Malabsorptive surgery – limits the amount of nutrients your body absorbs from your meals
  • Some procedures are both restrictive AND malabsorptive

Like any surgery, there are risks and benefits to consider before deciding whether to have the surgery. Talking with your healthcare professional about your specific situation is a good place to start.

Increasing Success Over the Long Term

Changing your habits is very difficult, especially when it involves eating and physical activity. But, with a plan, dedication, regular support, and patience, you can lose weight and improve your overall health. The following tips may help you think about how to increase your chances of success over the long-term.

  • Be prepared for setbacks, they are normal: After a setback, like overeating at a family celebration or workplace gathering, try to regroup and focus on getting back to your healthy eating plan as soon as you can.
  • Identify and prevent temptations: Think about the types of activities or situations that may cause you to overeat. Then consider strategies for how you can stay on track while still engaging in those activities, or how to prevent those situations altogether.
  • Track your progress: Sometimes it can feel like you are not making any progress at all. So, tracking your efforts can help you see the results of your hard work. There are many different online tools and mobile apps available that can help you track things like the foods you eat, your physical activity, and your weight. 
  • Set goals: Having specific goals can help you stay on track. For example, rather than “I’ll be more active,” set a goal to walk 15 minutes before work or at lunch on Monday and Friday. If you miss a walk on Monday, pick it up again Tuesday. Then build on your success by going for a longer walk and/or by adding an extra walk in your week.
  • Seek support: Ask for help or encouragement from your family, friends, or health care professionals. You can get support in person, through email or texting, or by talking on the phone. People often find they are more likely to follow their exercise routine if they have somebody to do it with. You can also join a support group or weight management program. Specially trained health professionals can help you shift towards healthier habits.

Questions to Ask

  • Do I have overweight or obesity?
  • How is my weight affecting my metabolic health?
  • How is my weight impacting my kidney disease?
  • Do any of my medicines increase my risk for weight gain? If so, are there any alternatives we can try or steps I can take to lower this risk?
  • Can you please refer me to a dietitian to help me develop a meal plan?
  • What kinds of physical activities are safe for me given my kidney condition and weight?
  • Can we please discuss the risks and benefits of weight loss medication for my situation? What about weight loss surgery?
  • Are there any support programs or specialists in my area that can help me with my weight loss journey?

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© 2024 National Kidney Foundation, Inc. This material does not constitute medical advice. It is intended for informational purposes only. Please consult a physician for specific treatment recommendations.