Factors Influencing Abdominal Obesity by Waist Circumference Among Normal BMI Population

Last reviewed: March 2026

Background and Context

Body mass index (BMI) has long served as the primary screening tool for overweight and obesity in clinical and public health settings. However, BMI has well-recognised limitations — it does not distinguish between fat mass and lean mass, nor does it capture the distribution of body fat. Abdominal or central obesity, characterised by excess visceral fat deposition around the waist, is a more potent predictor of cardiovascular disease, type 2 diabetes, and metabolic syndrome than overall body weight.

Waist circumference (WC) provides a direct, practical measure of abdominal fat distribution. International guidelines from the World Health Organization (WHO) and the International Diabetes Federation (IDF) have established WC cut-off values for abdominal obesity, though these thresholds vary by ethnic group. For Asian populations, the IDF recommends cut-offs of ≥90 cm for men and ≥80 cm for women — lower than the Caucasian thresholds of ≥102 cm and ≥88 cm — reflecting the increased metabolic risk associated with lower levels of central adiposity in Asian populations.

Malaysia presents a particularly compelling case for studying the BMI–WC discordance. The country’s multi-ethnic population — comprising Malays, Chinese, Indians, and indigenous groups — exhibits diverse body composition patterns. The National Health and Morbidity Survey has documented that Malaysian adults have high rates of abdominal obesity even when BMI falls within the normal range, a phenomenon with significant implications for cardiovascular risk screening.

The Normal Weight Central Obesity Paradox

Normal weight central obesity (NWCO) describes individuals who maintain a BMI within the normal range (18.5–24.9 kg/m² for general populations, or 18.5–22.9 kg/m² using Asian-specific cut-offs) but have elevated waist circumference indicative of excess visceral fat. These individuals may be overlooked in routine screening because their BMI does not trigger clinical concern, yet they carry cardiovascular and metabolic risks comparable to — and in some studies exceeding — those of individuals who are overweight by BMI criteria.

The mechanisms underlying NWCO include genetic predisposition to visceral fat accumulation, hormonal factors (particularly in postmenopausal women), physical inactivity with preserved dietary restriction (maintaining normal weight while losing muscle mass and gaining visceral fat), and ethnic-specific body composition patterns. South Asian populations, including Malaysian Indians, appear to be particularly susceptible to this phenotype.

Key Findings in the Malaysian Context

The study found that among Malaysians with normal BMI, a notable proportion met criteria for abdominal obesity based on IDF-recommended WC cut-offs. Female sex was strongly associated with abdominal obesity in this normal-weight group — a finding consistent with evidence that women tend to deposit proportionally more fat in the abdominal region after menopause due to declining oestrogen levels.

Age emerged as another significant predictor, with older adults more likely to exhibit the NWCO phenotype. This aligns with the well-characterised age-related shift in body composition, where lean muscle mass declines and is replaced by visceral adipose tissue, even in the absence of weight gain as measured by BMI.

Ethnic differences were also observed, with Malaysian Indian participants showing a higher prevalence of elevated WC among normal-BMI individuals compared to Malay and Chinese counterparts. This pattern is consistent with the broader literature on South Asian metabolic risk, which has documented higher visceral fat deposition, greater insulin resistance, and elevated cardiovascular risk at lower BMI thresholds in populations of South Asian descent.

Clinical and Public Health Implications

The findings strongly support the routine measurement of waist circumference alongside BMI in Malaysian clinical settings. The Malaysian Clinical Practice Guidelines for Obesity Management (2023 edition) recommends screening with both BMI and WC measurements, using cut-offs of ≥90 cm for men and ≥80 cm for women to define abdominal obesity. This dual-screening approach helps identify individuals with NWCO who would otherwise be missed.

From a public health perspective, health promotion campaigns in Malaysia should communicate that normal weight does not guarantee protection from metabolic disease. Messages about healthy body composition — emphasising the importance of waist measurements, physical activity to preserve lean mass, and dietary patterns that limit visceral fat accumulation — may be more effective than simplistic weight-focused messaging.

Limitations

The study’s cross-sectional design limits causal inferences. WC measurement, while practical, does not directly quantify visceral adipose tissue — CT or MRI imaging would provide more precise assessment but are not feasible for population-level screening. The study did not assess metabolic biomarkers (such as fasting glucose, lipid profiles, or insulin levels) that would confirm whether the elevated WC in normal-BMI individuals was associated with actual metabolic dysfunction. Sample size and selection methods may limit generalisability to the broader Malaysian population.