What are the factors affecting BMI?

BMI calculation

BMI can be calculated by using a formula or by using a BMI chart.

The formula of BMI is:

BMI= Weight (kg)/Height (meters) 2

Clinical importance of BMI

As BMI is the indicator of total body fat, it is considered a risk of many health complications.

BMI values are used to assess an individual’s health issue associated with obesity by many healthcare professionals.

Individuals with high BMI values are at risk for many diseases and health conditions, including the following:

  • Hypertension
  • High cholesterol level
  • Type 2 diabetes mellitus
  • Coronary heart disease
  • Stroke
  • Disease of gallbladder
  • Osteoarthritis
  • Sleep disorder
  • Chronic inflammation and oxidative stress
  • Low quality of life
  • Mental disorders including depression, anxiety, and other mental illness
  • Difficulty in physical functions

Obesity and other risk factors of non-communicable diseases are emerging in developing and developed countries. Strategies to reduce the burden of obesity depend on understanding and recognizing this complex disease. Healthcare professionals are advised to diagnose these complications in obese individuals and spread awareness of weight loss in them.

Factors that affect the BMI of an individual

Many factors are affecting BMI and lead to obesity or overweight. The individuals cannot control some of these factors such as developmental factors, genetic factors, gender, and age. Other factors that affect the Body Mass Index can be controlled such as, physical activity, diet, environmental factors, and social factors. The risk factors, associated with a high value of BMI, were described in the research paper “The Epidemiology of Obesity: A Big Picture” published in 2015.

Body Mass Index (BMI) is the measurement of an individual’s weight in kilograms divided by the square of height in meters. BMI is related to the body fat of a person. It means if the BMI score is high, so does the total body fat.

According to CDC BMI individuals with BMI:

  • below 18.5 are underweight
  • 5-24.9 are healthy
  • 0-29.0 are overweight
  • 0 and above are obese
Factors affecting BMI

Individual risk factors


The vast majority of research on high BMI or obesity risk factors is now focused on individual behaviors. It is found that diet and physical activity play a vital role in mitigating high BMI risk and its prevalence. In clinical and weight management approaches, the main focus is on calorie restriction.

Various clinical trials have proved that calorie restriction results in better weight loss outcomes regardless of dietary patterns.

Healthy dietary habits lead to long-term maintenance of a healthy weight. A healthy diet such as vegetables, fruits, whole grains, nuts, and yogurt play an important role in the maintenance of a healthy weight as compared to an unhealthy diet such as potato chips, sugar-sweetened beverages, and processed food.

Physical activity

Recent studies have shown that 150-250 minutes per week of intensive physical activity is required to prevent weight gain. It also aids in weight loss when combined with dietary restrictions. Physical activity less than 250 minutes per week is associated with weight loss and maintaining weight after losing it.


Sedentary lifestyle, and Sleep

Leisure-time activities such as sitting for a long time, television viewing, or screen time also contribute to gaining weight. A good 6-8 hour sleep for adults is also important in maintaining weight. Too much and too little sleep is associated with weight gain.


Smoking and alcohol

The metabolic rate is increased after smoking and it can limit the intake of food. This results in increased BMI. Consuming alcohol has also an impact on body weight. Energy consumed in the form of alcohol is converted to fat and stored in the body.


Many drugs are one of the factors affecting BMI. These drugs include:

  • Hypoglycemic agent (insulin)
  • Antihypertensive agents
  • Anti-allergens
  • Anti-psychotic drugs

Prenatal influences

Early life is also important. Children of pregnant women who smoke and are obese are more likely to be overweight adults.

It is also documented that females who are severely malnourished during early pregnancy have kids with a higher risk of obesity, diabetes, resistance to insulin, and high blood pressure later in life.

Environmental factors
Environmental pathogens


It is evident through different animal and human studies that infection may be one of the factors associated with obesity. Studies in the human population have proved that human adenovirus-36 is the cause of obesity in both kids and adults.


It is also coming to light that some gut bacteria contribute to obesity, energy metabolism, and digestion of carbohydrates and lipids. The population of the microbiome, in lean and obese individuals, differ, these numbers change when obese individuals lose weight. Changes have been observed in patients after gastric bypass surgery.

Social network

In 2007, a study examining the spread of obesity due to social ties, shows that chances of gaining weight in person increased by 57% if his or her friend gain weight in a given 4-years interval.

Built environment

Inbuilt environment studies scientists focus on a few measurable characteristics of a neighborhood that are related to weight status. However, the focus should be on diet-related built environments rather than those associated with physical activity.

Physical activity or recreational activities are associated with increased physical activity or energy expenditure and a healthy food environment is characterized by the availability of organic produce and the presence of supermarkets over convenience stores or fast food points. Studies show that a healthy food environment is one of the important factors affecting BMI.

Socioeconomic factors

Family and ethnicity

Eating is a social activity and many eating habits are acquired in family or ethnic settings. Many people tend to have the same eating habits as their parents, that’s why quantity and quality of food eaten tend to establish early.

Dietary changes are strongly associated with increased weight as people tend to acquire the habits of the people they live with.

Socioeconomic status

Data suggest that income and education are linked with obesity. In some countries where the economic situation of people is good, the rate of obesity is high. Also, in some countries where the poverty rate is high, a large number of people are obese and have high BMI values. Data also show that education plays an important role too. Educated individuals mostly maintain a healthy lifestyle and have a healthy weight. In this changing economy, education may change the negative effect of the increase in purchasing power in emerging obesogenic environments.

Obesity is a major contributor to serious health issues and death across the globe. Decrease in physical labor, automated transportation, sedentary lifestyle, and unhealthy diet choices have made this once rare disease into a most common disease. Healthcare expenditure can be reduced if we can decrease the childhood obesity trends and if young and middle-aged overweight and obese people lost 10 % of their body fat.

So, there is an urgent need for a deeper understanding of risk factors affecting BMI and possible solutions for this epidemic.