Defining Overweight and Obesity: Causes, Consequences, and Tips

by Marixie Ann Obsioma, MT, undergrad MD on May 26, 2021
Last updated on May 28, 2021

Being overweight or obese is often referred to as behavioral issues. However, in today’s modern world, experts have started to view obesity as an actual disease (1). In fact, it has become an epidemic in the US, affecting more than 93 million adults and a little less than 14 million kids and teenagers (2, 3).

Defining Overweight and Obesity - Causes, Consequences, and Tips

Overweight and obesity are two terms that are often used in close relation to one another. They get thrown a lot with many people not realizing that they have their own clinical definition and a number of differences. While both of them are used to describe excess weight in the human body, one may wrongly refer to an overweight individual as obese and vice versa.

So what is the difference between the two? Let’s discuss the basics!

What Is Body Mass Index (BMI)?

Body Mass Index (BMI) is used to make a surrogate measure of body fat based on weight and height using a standard equation. It helps determine whether one is at a healthy or unhealthy weight. It is simple, cheap, and non-invasive. One can routinely measure and calculate his or her BMI with reasonable accuracy.

Furthermore, studies have shown that BMI levels correlate with body fat and with possible health risks (4). Both high and low BMIs can cause health problems. A high BMI is often associated with high blood pressure, heart disease, stroke, diabetes, and cancer. On the other hand, a very low BMI may cause anemia, decreased immune function, and bone loss.

The widespread and long-standing use of BMI has helped produced data that allows healthcare professionals to make comparisons across time, regions, and population subgroups. BMI is indeed a helpful screening tool for bodyweight problems, but it does have limits, which will be discussed in detail below.

How Do You Compute For Your BMI?

As mentioned earlier, your BMI is calculated using a standard formula. It is your weight in kilograms divided by your height in meters squared.

  • Weight (kg) / [Height (m)]2

If your height has been measured in centimeters, you have to divide it by 100 to convert to meters.

If you want to use English measurements, pounds should be divided by inches squared. After which, multiply it by 703 to convert from lbs/inches2 to kg/m2.

  • 703 x Weight (lbs) / [Height (in)]2

You may also take advantage of CDC’s simple online BMI calculator for kids, teens, and adults (5, 6). While the calculation is similar for people of all ages, it is interpreted differently for kids and adults.

BMI and Weight Status

People age 20 and above are considered adults. Their BMI should be interpreted as follows, regardless of gender and body types:


Weight Status

Below 18.5






30.0 and above


For people under age 20, BMI is interpreted differently. While the same equation is being used for calculation, the implications for kids and teenagers may vary depending on gender and age. Girls normally have a higher amount of body fat and develop it earlier than boys.

The CDC recommends the use of age growth charts for kids and teens to show BMI as a percentile ranking (7). Each percentile expresses a kid’s BMI relative to other kids of the same gender and age. For instance, a kid should be considered obese if he or she had a BMI that landed at or above the 95th percentile. This means that he or she has more body fat than 95% of kids in the same gender and age category.

Here’s the percentile range for each weight status:


Weight Status

Below 5th






95th and above


So basically, overweight is defined as having a BMI that landed at the 85th-95th percentile for kids and teens or 25 to 29.9 for adults. Obesity, on the other hand, is getting a BMI at the 95th percentile or above for kids and teens and 30 and above for adults.

What Are the Limitations of BMI?

As mentioned earlier, BMI has clinical limitations. Factors like age, sex, ethnicity, and muscle mass can greatly influence the relationship between BMI and body fat. Also, BMI cannot distinguish between excess fat, muscle, or bone mass, nor does it give any indication of fat distribution among individuals. Listed below are some examples of how certain variables can affect BMI interpretation:

1. Age and Gender

For adults ages 20 and above, BMI incorporates weight and height, but it does not take age or gender into consideration. Women tend to have more body fat than men with the same BMI. Also, older people are expected to have more body fat than younger individuals with an equivalent BMI.

2. Body Composition

BMI cannot reflect the location or amount of body fat, and these can greatly impact health. Studies have shown that those who have excess fat around the waist, surrounding abdominal organs are at a greater risk of health problems that those with fat in other locations (8).

Did you know that it is also possible to be overweight, but have healthy levels of fat? For extremely muscular people like athletes and bodybuilders, height and weight measurements alone may not accurately indicate health since muscle weighs more than fat.

A healthy, muscular person can have a BMI in a very high range. On the other hand, a frail and inactive person may have a low BMI, but more body fat and less lean tissue than is healthful.

3. Races and Ethnicities

The norm for BMI measurement and interpretation may also vary among people of certain races and ethnicities.

4. Stages of Development

BMI can also not accurately indicate the state of an individual’s health at some stages in life, such as pregnancy and breastfeeding.

The issues associated with using BMI for adults also apply to kids and teens. Other factors such as height and level of sexual maturation can affect the relationship between BMI and body fat among kids too. Also, the accuracy of BMI may vary substantially according to a child’s degree of body fatness. Among obese kids, BMI is a good indicator of excess body fat. However, for overweight kids, elevated BMI levels can be a result of increased levels of either fat or fat-free mass. Similarly, among thin kids, differences in BMI are often due to differences in fat-free mass.

Are There Any Other Measures of Body Fat Available?

Aside from BMI, research suggests the use of skinfold thickness, underwater weighing, dual-energy x-ray absorption, and bioelectrical impedance to measure body fat. While these are believed to be more accurate than BMI, they are not as easy and convenient. Some are expensive and can be invasive.

Other ways and signs that are easier to use and understand as a BMI reading include:

1. Waist Measurement

One of the best ways to tell if you are at a healthy weight is from your waist measurement. A waist circumference of greater than 35 inches in women and more than 40 inches in men does not only confirm an overweight status but also add a hard-and-fast number on one’s health (9). These numbers clearly indicate excessive belly fat, which is dangerous as it surrounds vital organs.

This tool is straightforward to perform and is a rather reliable predictor of risk for hypertension, type 2 DM, and heart disease. All you need is a measuring tape! Place it on top of your hip bone, bring it around your body at the level of your belly button. Do not suck in or make the tape too snug. A false reading only hurts you!

2. Snoring

Is your partner snoring? How about you? Excessive snoring and waking up restless is an indication that it’s time for you to check your weight!

When you have excess body fat around your neck, there will be narrowing of the airway. You’ll experience shallow breathing or pauses in breathing while sleeping, which may cause loss of oxygen and extreme fatigue during waking hours. This condition is more commonly known as sleep apnea.

3. Frequent Heartburn

Changes in your body weight, even the slightest ones, can cause you to have acid reflux. More than 1/3 of overweight and obese people experience gastroesophageal reflux disease (GERD). Evidence suggests that there is a direct association between being obese and the development of GERD (10). Other symptoms of this disease include nausea, belching, bitter taste, and abdominal pain.

4. Achy Joints

Obesity is a risk factor for osteoarthritis, a disabling disorder that may lead to pain, decreased joint mobility, and joint deterioration. Carrying around extra weight applies more pressure on all of your joints, thus causing you to have chronic back pain and achy hips or knees.

What Are The Most Common Causes of Overweight And Obesity?

A lot of people think that weight gain and obesity are caused by a lack of willpower. This is not entirely true. Although weight gain is largely a result of unhealthy eating patterns and lifestyle, others are at a disadvantage when it comes to controlling their habits.

Overeating can be driven by several biological factors, including genes and hormones. Some people are simply predisposed to gaining excess weight (11). While it is possible to overcome genetic disadvantages by changing your lifestyle and behavior, it will require willpower, perseverance, and dedication.

Listed below are some of the leading causes of weight gain, obesity, and other metabolic diseases. Most of which have nothing to do with willpower.

1. Genes

Obesity has a very strong genetic component. Kids of obese parents are more likely to become obese as compared to kids of lean parents. However, this does not mean that weight gain is completely predetermined. Genes may affect your susceptibility to gaining weight (12), but what you eat can have a major effect on which genes are expressed and which are not.

2. Engineered Junk Foods

Heavily processed foods primarily consist of refined ingredients and additives. These products are designed to be cheap, long-lasting, and taste so good that they are quite hard to resist. Manufacturers increase their sales by making their food tasty, but this also encourages overeating.

3. Food Addiction

Foods that contain high amounts of fat and sugar often stimulate the reward centers in your brain (13, 14). In fact, they are often compared to commonly abused drugs such as alcohol, cannabis, cocaine, and nicotine.

These junk foods can cause addiction in susceptible individuals. People tend to lose control over their eating behavior, similar to those struggling with drug and alcohol addiction.

4. Aggressive Advertising and Misinformation

Junk food manufacturers are also aggressive marketers! Sometimes, their approaches are even unethical, marketing very unhealthy products as good. They also make misleading claims, which are specifically targeting children.

5. Insulin

Insulin is one of the most important hormones in the body. It regulates energy and fat storage. Some diet promotes insulin resistance, which prompts your body to store energy in fat cells instead of making it available for use (15). Evidence suggests that high insulin levels may have a role in the development of obesity (16).

To lower your insulin levels, cut back on simple and refined sugar and increase your fiber intake (17). This will also reduce your calorie intake, which will help you lose weight.

6. Medications

Diabetes medications and antipsychotics can cause weight gain as a side effect (18, 19). Antidepressants have also been associated with modest weight gain over time (20). They either reduce your metabolic rate or increase your appetite (21, 22).

7. Leptin Resistance

Leptin is yet another hormone that plays a huge role in obesity. It is produced by fat cells and its level increases with higher fat mass. For this reason, obese people have elevated leptin levels.

In healthy individuals, high leptin levels can actually help curb appetite. When working properly, it tells your brain how high your fat stores are. The problem is that leptin isn’t working as it should in obese patients. One reason is that it isn’t capable of crossing the blood-brain barrier (23). This condition is known as leptin resistance and is thought to be a leading factor in obesity.

How Does Excess Weight Affect Your Body?

People who have excess weight, especially those who are obese have high chances of developing serious health issues. These problems affect nearly every part of your body, including the heart, blood vessels, brain, bones, liver, gallbladder, and joints. Here’s a sneak peek of how obesity can affect your overall health.

  • Risk of Stroke. Obesity is a risk factor for ischemic stroke. This association is mediated by hypertension, diabetes, and other variables associated with these conditions (24).
  • Increased Risk of Heart Attack. Aside from high blood pressure, high blood glucose and cholesterol levels can harden your arteries, thus increasing your risk of a heart attack.
  • Type 2 DM. Excess weight and body can make your body resistant to insulin. This will increase your blood glucose level and your risk for type 2 diabetes (25).
  • Gastroesophageal Reflux (GERD). Obesity has been associated with a greater risk of GERD, where stomach acids leak into your esophagus (10).
  • Liver Disease. Excess fat can accumulate around your liver, causing damage and failure. Steatosis occurs when there are more fatty acid production and uptake from the plasma than oxidation and export. An excessive amount of intrahepatic triglyceride will cause an imbalance in metabolic events (26).
  • Gallbladder Problems. Obesity may increase your risk of developing gallstones, which may need surgery. This is mostly due to the supersaturation of bile with cholesterol, because of increased production by the liver and secretion into bile (27).
  • Kidney Failure. To compensate for the increased metabolic demands brought about by weight gain, a compensatory hyperfiltration occurs in obese individuals. There will be an increase in intraglomerular pressure, which can cause damage to the kidneys and increase your risk of developing chronic kidney disease in the long run (28).
  • Sleep Apnea. Excess fat around the neck area can narrow your airways, causing your breathing to stop for periods of time at night (29).
  • Skinfold Rashes. Obesity is a risk factor for the formation of discolored and thickened rashes on skin folds and creases known as intertrigo (30).
  • Increased Depression. Being overweight or obese can also affect your mental health. You’ll have issues with your body image, thus increasing your risk of depression.
  • Infertility and Pregnancy Problems. Obesity will make it hard for you to get pregnant. Also, it has been associated with unfavorable clinical outcomes for both mother and child, such as gestational diabetes, pre-eclampsia, and even intrauterine death of babies (31).
  • Weakened Muscles and Bones. Excess weight may cause muscle mass and bones to deteriorate, leading to fracture and disability risks.
  • Joint Pain. Extra weight can put a strain on your joints, causing stiffness and pain.
  • Cancer. Obesity has been associated with cancer. The prevalence and possible mechanisms vary widely for different cancer types (32).

Can You Prevent Weight Gain and Obesity?

Whether you are at a healthy weight or at risk of becoming overweight or obese, there are steps and tips you can follow to prevent weight gain.

Eat Healthily

Create a healthy eating plan by focusing on nutrient-packed, low-calorie foods like fruits and vegetables. Steer clear from saturated fats, sugary foods, and alcohol.

Engage in Regular Workouts

You can prevent weight gain if you allot time for exercise. The early morning hours are ideal. Make exercise part of your daily life to help burn excess fat.

Monitor Your Weight Regularly

Keeping an eye on your weight regularly can help keep off excess pounds. Detecting small weight gain before it becomes a bigger problem can be very helpful.

The Bottom Line

While obesity is considered to be more serious than overweight, both can affect nearly all parts of your body. To live healthily, you must treat or manage these risk factors with lifestyle changes, which include diet and exercise. Also, losing as little as 5-10% of your current weight can help reduce your risk of developing serious health issues. Talk to your doctor about losing weight and maintaining a healthy lifestyle!


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