Global life expectancy for both sexes increased from 65.3 years in 1990 to 71.5 years in 2013.

At the same time, the prevalence of obesity nearly tripled between 1975 and 2016, giving it a global epidemic status.

Globally, from 108 million diabetes cases in 1980, the number of diabetics rose to 422 million in 2014. The majority of these cases is affected by type 2 diabetes.

The former is good news, but the twin epidemics of obesity and diabetes dims the prospects of the former – meaning that as the prevalence of these two conditions grows, the life expectancy of the global population will go on decreasing.

Obesity is defined as the excess deposit of fat in the body. The fat could exist centrally around the abdomen and chest or it could be on the thighs and the hips (peripheral obesity).

It is the central obesity, which poses serious health risks and curtails the lifespan of the person. The peripheral obesity is not so dangerous.

Therefore, along with the BMI, measuring the waist circumference is important to determine if the person is at a risk of obesity complications and reduced lifespan.

Women with a waist circumference of 35 inches and above and men with an abdominal girth of 45 inches and above invite significantly high risks.

The health complications of obesity span across all body systems and can lead to serious issues such as heart disease and stroke. Most of these conditions in an obese person are fatal.

The obese person, therefore, faces a shorter lifespan than a person with a healthy weight does, because of what obesity can do to you.

This post probes the relation and explains how obesity reduces the lifespan. It also probes into the details of the life expectancy of an obese smoker and an obese diabetic.

Effects of smoking and obesity on life expectancy

The obesity mortality rates are significantly higher when the obese person is a smoker. The life expectancy drops by almost half when an obese person also smokes. This is because the effects of smoking compound the effects of obesity.

As a general rule, for every pound or half a kilogram (approx), you are overweight, your life reduces by about one month.

Given below is a chart, which compares the drop in life expectancy of being overweight and obese in a smoker and nonsmoker, both in males and females.

Overweight is considered at a BMI of 25 to 30 kg/m² while obesity is BMI of more than 30 and the comparison is at age of 40 years and with nonsmoking people of normal weight.


  Females Males
Overweight and non smoker -3.3 years -3.1 years
Obese and non smoker -7.1 years -5.8 years
Overweight and smoker -7.2 years -6.7 years
Obese and smoker -13.3 years -13.7 years

Below are the death rates in morbidly obese people with reference to ethnicity.

  • White men aged between 20 years to 30 years with a BMI more than 45 (morbidly obese) could shorten their life by 13 years.
  • White women in the same category could shorten their life by 8 years.
  • African-American men in the same category could lose 20 years of life.
  • African-American women in the same category could lose up to 5 years of life.

Obesity and life length are inversely related and obesity does lower the lifespan. In other words, obesity and mortality are strongly connected. The more the person is obese, the higher is his mortality risk.

This is how obesity and its risks are classified in relation to the BMI. It is presumed that the obesity is of the central type.

  • Overweight with BMI of 25.0 to 29.9: Risk exists but low as compared to obesity.
  • Class 1 obesity, if BMI is 30.0 to 34.9: Risk higher than overweight.
  • Class 2 obesity, if BMI is 35.0 to 39.9: Moderate risk
  • Class 3  obesity, if BMI is equal to or greater than 40.0: High risk.

Class 2 obesity with moderate risk, which is now more common, reduces life expectancy by about 3 years.

Severe obesity, also referred to as morbid obesity, with BMI = or > 40.0, which is uncommon, can shorten a person’s life by 10 years. This is equal to the period reduced by lifelong smoking.

The healthiest BMI with the lowest mortality is between 23 and 24.

The obese diabetic and his life expectancy

The obese diabetes patients are at a high risk of losing many years of their life besides incurring heavy medical expenses.

To make matters worse, both these health conditions have achieved epidemic proportions worldwide.

More than 90% of type 2 diabetics are overweight or obese, making excess weight the major independent contributor to diabetes type 2.

According to, you could reduce your life expectancy by 8 years and your healthy life by 19 years if you are associated with obesity and diabetes.

According to data from the U.S. National Health Interview Survey for 1997 to 2000, diabetic white females with a BMI >40 kg/m(2) had 17.9 remaining life years, whereas diabetic white females with normal weight had 22.2 remaining life years and lifetime health expenditure.

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