Obesity vs. Overweight: What Is The Difference?

by Rakib Sarwar, RPh
Published on July 3, 2019

Today, more people are overweight and obese than ever before. Unfortunately, the problem has become common in children. Obesity and overweight are terms used to identify and describe people who are prone to health problems due to excess accumulation of body fats.

It is no doubt that everyone needs some body fat for energy, heat insulation, and other body functions, but accumulating excess fat in the body leads to serious health problems. That is to say, the more fat one accumulates, the greater the risk of having critical health issues. Many factors contribute greatly to weight gain and go on to affect how much fat your body stores.

Let us briefly discuss how our body makes use of the calories we consume in a layman’s language; the calories we get from the food we consume helps the body in performing its functions as mentioned earlier. When one takes more calories from food than one uses up from all the daily physical activities, the body stores the unused extra calories. Over time, if one goes on to consume more calories than the body needs, then weight gain becomes easy. Excessive gaining of weight may now lead to overweight or obesity.

Attaining and maintaining a healthy weight may be a long term challenge if you are overweight or have obesity. If you are already overweight or have obesity, maintaining a healthy weight and not gaining more weight can go a long way in helping you lower the chances of developing associated health problems.

The health problems that can develop from obesity and overweight are diabetes, high blood pressure, stroke, kidney diseases and failures, heart diseases, arthritis and more.

The terms overweight and obesity get thrown around a lot with most people not realizing that the two words actually have their clinical definitions and a number of differences. One might wrongly refer to an overweight individual as obese and vice versa.

So, how do we differentiate these two terms? Though the two words obviously are part of a disease process caused by too much accumulation of fats in the body, there is definitely a medical definition for obesity as well as for the term overweight.


Being overweight has become a serious worldwide concern both in kids and adults. A healthy body system needs a required amount of body fat for adequate functioning of the immune system, energy for future use, hormonal and reproductive activities. When the body fat is accumulated, health becomes impaired and may, as a result, lead to significant long term health consequences. Besides internal health issues, overweight also alters the physical appearance of the body.

Overweight is generally referred to as the body weight that is higher than what is considered to be healthy for a certain height. Simply put, overweight is basically due to the accumulation of extra body fat as mentioned earlier.

In other cases, overweight may also be as a result of extra muscle, bone or even water.

In medical terminology, overweight can be defined based on body mass index (BMI).

An individual’s body mass index is one way to tell if one is at a healthy weight, overweight or have obesity. That is to say, the degree to which a person is overweight is generally described by the body mass index (BMI) (5).

Body mass index requires the height and weight of the individual for the calculation. It is a measure of a person’s weight taking into consideration the person’s height. It is mathematically given as the weight of the person in kilograms divided by the square of the person’s height in meters (2).

Therefore, the body mass index is measured in units of a kilogram per meter squared (kg/m2). The value of BMI is typically used and written without units (1).

This method of using body mass index to determine the degree of overweight of an individual provides a more accurate representation of fat in a body compared to just measuring the weight of the person (5).

It is pertinent to note that BMI does not take into consideration some factors such as pregnancy or bodybuilding.

It is a manual process to check for BMI, this makes it very simple and easy that anyone can use it to determine health risk due to excess body fat levels. The BMI calculators are readily available. One only needs to get the values of weight and height. By using the formula, you can interpret your BMI results (5).

Interpretation of BMI

Using the simple chart below, you can interpret your BMI result. For adults, BMI results are interpreted as shown below;

  • Underweight= BMI below 18.5 (1)
  • Normal weight= BMI between 18.5 – 24.9 (1)
  • Overweight= BMI of 25.0 – 29.9 (1)
  • Obese= BMI of 30.0 and above (1).

The above chart is for adults. In children, BMI is interpreted differently. This is because children are still growing and boys and girls grow and mature at different rates. This is why growth charts and percentiles are used so that age and gender are taken into account.

If the BMI falls between 85th to less than 95th percentile, then the child is overweight (1, 3).

If it is in the 95th percentile or greater, the child is considered to be obese (3).
Ok, let us give an example of how BMI is calculated.

Remember the formula is weight (kg)/Height2 (m2) (1)

If the weight, for instance, is 80kg and height is 170cm which is equivalent to 1.7m
Then, the BMI is 80/1.72
= 80/2.89
BMI = 27.68 (1)

Using the chart, the result above shows that this individual is overweight. It is as simple as that.

Even though there is a strong correlation between BMI and body fat measurement, there are some limitations which are based on the person’s age, gender, and athletic ability (3).

  • In terms of gender, women tend to have more body fat than men (1).
  • Older people tend to have more body fat than younger adults (1).
  • Highly trained athletes have higher muscle mass rather than body fat. This increases their body weight measurement hence high BMI. Therefore, BMI formula cannot be used to calculate the degree of weight in them as the BMI number cannot distinguish the various components that make up the total body weight. Simply put, these athletes may have a BMI that identifies them as being overweight even though they do not have excess body fat.

Being overweight has a strong correlation with developing serious health issues. This is the reason why BMI is used in screening the health of the general population.

Another tool used in determining the degree of overweight is the body volume index (BVI). Unlike BMI that is manual, BVI is devised as a computer that uses 3D software to create an accurate image of a person. This tool measures the location of weight and fat in the body especially the weight and fat carried around the abdomen.

Another tool used is a simple weighing method. This is the easiest and the most common method but the least accurate as it only measures the weight. It does not take into consideration the height of the person, body type or muscle mass.

With this method, a person’s weight is measured and compared to an estimated ideal weight.

People who are overweight have increased the risk of developing health conditions like; hypertension, type 2 diabetes, heart diseases, stroke some cancers, kidney problems, breathing problems, arthritis, gallbladder disease, and respiratory problems (4).


Obesity is a medical condition and a complex disorder in which excess fat has accumulated to an extent that it may result in serious health conditions. Obesity is not just a cosmetic concern. Being obese means you are highly likely to have health problems related to your body weight.

The bad thing about obesity is that it is a disease caused by many factors which we will be discussing soon. It has become a worldwide concern but the good news is that it is treatable and manageable. That you are obese does not mean it is your fault, it is also not about weight gain by food consumed and it is not yours to manage alone. Healthcare providers and other trained personnel are available to help through the prescription of medications and weight loss surgery.

Body fat is not simple to measure directly. So, BMI is often used to determine how obese one is. It is still the same method used for calculating how overweight someone is. That is, dividing the body weight (mass) in kilogram by square of the height (1).

The only difference is the range of the BMI value (1).

Therefore, a BMI that falls in the range of 30.0 to 39.9 indicates obesity (1).

How do we then describe someone with a higher BMI value? Someone who is more than 100 pounds has a BMI greater than 40 and this condition is referred to as severe obesity (3).

There is also the class I, II and III obesity. These are severe cases of obesity and should be treated as an emergency to avoid the high risk of medical problems (3).

Below is a chart that shows the classifications of obesity and the corresponding BMI range.

  • Class I obesity 30.0 – 34.9
  • Class II obesity 35.0 – 39.9
  • Severe obesity 40.0 and above (1, 3).

BMI is not a percentage of the body fat but only a part of a diagnosis of obesity.
As discussed earlier, BMI does not directly measure body fat, therefore, it is not a good tool for determining obesity in muscular athletes. This is because these athletes may have a BMI in the obese category even though they don’t have excess muscle mass and not excess body mass.

Causes of obesity and overweight

A lot of factors are causes of obesity and overweight; genetic, behavioral and hormonal factors. Basically, obesity or overweight occurs when one takes in more calories than one burns through exercise and other normal daily activities. It is natural that the body stores these excess calories as fat.

Generally, the principal causes of obesity and overweight are discussed below.

  • Unhealthy diet and eating habit. Eating more calories than the body needs makes weight gain inevitable. Most foods consumed every day are high in calories. For example, beverages, fast food, fried foods, sugary foods, etc.
  • The stored fat in the body that leads to overweight or obesity is the excess one stored as calories. If one is not active, calories won’t be burnt. Over time, calories accumulate and lead to overweight or obesity.
  • There is also a risk factor that involves the genes negatively affecting the storage and distribution of body fat in the body. So, genetics may play a necessary role in the conversion of food into energy and how the body burns calories during exercise and day to day activities
  • Family lifestyle. Overweight and obesity tend to run in families. Genetics might not play any role here but the fact that family members tend to share similar eating and activity habits places them at the risk of being overweight or obese.
  • These conditions can occur at any age; young or old. As one age, one becomes less active and will not be able to burn calories as when he or she was younger. Also, hormonal changes as one age increase the risk of overweight and obesity.
  • Lack of sleep. Lack of sleep causes hormonal changes that increase your appetite thereby making you consume foods high in calories.

Having one or more of these risk factors doesn’t mean that you are bound to become overweight or obese. A healthy diet, physical activity, and exercise go a long way in counteracting most of these risk factors.


Whether you are at a healthy weight or at risk of becoming overweight or obese, you can take the necessary steps to prevent weight gain.

Eat healthily

Maintain a healthy eating plan by focusing on low-calorie, nutrient dense foods such as fruits and vegetables. Stay away from saturated fats, alcohol, and sweet foods. Stick to foods that promote healthy weight and good health.

Engage in daily workouts

You can escape both obesity and overweight if you take out time to engage in daily workouts. Find a specific time of the day to engage in physical exercises. The early morning hours are ideal for this. Making daily workouts part of your life helps you burn excess fats.

Monitor your weight regularly

This will help you in keeping off excess pounds by helping you detect small weight gain before they become big problems.

To achieve a long term success in preventing overweight and obesity, remain consistent. Maintain your healthy weight plan at all times.


(1) https://www.who.int/publications/cra/chapters/volume1/0497-0596.pdf
(2) https://www.who.int/dietphysicalactivity/media/en/gsfs_obesity.pdf
(3) https://www.cdc.gov/ncbddd/disabilityandhealth/documents/obesityFactsheet2010.pdf
(4) https://www.mdpi.com/1660-4601/7/3/765/pdf
(5) https://www.rki.de/EN/Content/Health_Monitoring/Health_Reporting/GBEDownloadsJ/FactSheets_en/JoHM_2017_02_Overweight_obesity_adults.pdf?__blob=publicationFile

Read Next
Diet soda or diet drinks are advertised as a healthier…