The prevalence of normal weight obesity in a south Asian population was assessed in a study using data from baseline survey of the Kerala Diabetes Prevention Program (KDPP). A total of 1147 individuals, aged 30-60 years, at high risk of diabetes (IDRS >60) were included in this analysis. IDRS or the Indian Diabetes Risk Score uses four parameters to predict the risk of diabetes in the Indian population: age, presence of abdominal obesity, family history of diabetes and levels of physical activity.

Normal weight obesity was defined as body mass index (BMI) within the normal range (18.5–24.9 kg/m²) and a high body fat percentage (≥ 20.6% in men and ≥ 33.4% in women) and the overtly obese as BMI ≥25 kg/m² regardless of the body fat percentage. Those with normal BMI and body fat percentage (<20.6% in men and < 33.4% in women) were categorized as non-obese.

Almost one-third (32%) of the study participants was found to have normal weight obesity. Almost half of them (51%) had overt obesity, while 17% were non-obese. Nearly 20% of those with normal weight obesity had type 2 diabetes; 18.7% of obese had diabetes, while only 8% of the non-obese participants had diabetes.

The study also looked at the cardiometabolic risk profile of persons with normal weight obesity.

The prevalence of hypertension and pre-hypertension was significantly higher in individuals with normal weight obesity vs the non-obese; 15.3% and 50.8% vs 7% and 38.5%, respectively. About 89% of those with normal weight obesity had dyslipidemia vs 87.8% with obesity vs 75% in the nonobese. Additionally, the levels of mean serum total cholesterol, triglyceride and LDL cholesterol were considerably higher, while the mean serum HDL level were significantly lower in participants with normal weight obesity than in the non-obese participants.

These results show that one-third of the study population had normal weight obesity. They also had higher prevalence of cardiometabolic risk factors. Another notable finding was that two-third of those with a non-obese BMI had a high body fat percentage. The risk of developing type 2 diabetes, hypertension and dyslipidemia was about 2-fold higher in individuals with normal weight obesity as compared to non-obese individuals even after adjusting for age, sex, tobacco use and alcohol intake.

Obesity is a well-established risk factor for type 2 diabetes. Globally, the prevalence of obesity has increased much more than before and so has type 2 diabetes, almost hand in hand. A sedentary lifestyle including consumption of a high-calorie/high-fat and high sugar diets are major contributing factors.

India is only next to China in terms of the number of people with diabetes; 77 million vs 116.4 million respectively (IDF Atlas 2019). This number is projected to increase to 101 million in 2030 and 134.2 million in 2045. India also has nearly 44 million with undiagnosed diabetes. However, obesity is relatively not so prevalent in India vis-à-vis the western world, though the numbers are rapidly increasing. The differences in body composition and distribution of body fat in the otherwise apparently lean Indian phenotype may be the reasons for this discrepancy in prevalence.

The typical Asian Indian phenotype is the “thin-fat Indian” with smaller muscle mass, but more body fat compared to their white or African counterparts or other Asian ethnic groups. This is evident as central obesity with high waist-to-hip ratio (WHR), waist circumference and visceral fat. Therefore a person can still be obese even if the body weight is normal (normal weight obesity), where the BMI is normal as per the age and height, but the body fat percentage is high. Typically, such individuals have a potbelly but otherwise appear normal.

Abdominal obesity is more dangerous than generalized obesity as is evident by the clustering of the cardiometabolic risk factors.

BMI is the most commonly used measure of obesity. It takes into consideration height and body weight, but not body fat. A correct measure of obesity therefore is via measurement of body fat, especially the abdominal fat. Waist circumference is the simplest and an inexpensive way to measure this fat.

It, therefore, becomes important for primary care physicians to be aware of normal weight obesity and that fact that measurement of body fat percentage does not require any sophisticated tools. A simple measuring tape will help. Screening for body fat percentage in persons with normal body weight will help in the timely identification of those at risk of cardiac events.

(Source: Kapoor N, et al. Prevalence of normal weight obesity and its associated cardio-metabolic risk factors - Results from the baseline data of the Kerala Diabetes Prevention Program (KDPP). PLoS One. 2020 Aug 25;15(8):e0237974).

Dr Nitin Kapoor, Professor of endocrinology, Dept. of Endocrine, Christian Medical College, Vellore

Dr Sanjay Kalra, DM, Bharti Hospital, Karnal; Immediate Past President, Endocrine Society of India