Belly fat: 6 real causes and which tests to take

Belly fat is two very different things — subcutaneous (harmless) and visceral, which surrounds internal organs and is one of the strongest predictors of cardiovascular disease. Visceral belly fat cannot be simply exercised off without addressing the metabolic cause.

The two types

Subcutaneous fat is cosmetic. Visceral fat is metabolic — it releases inflammatory cytokines (IL-6, TNF-α), drops insulin sensitivity and is an independent heart-attack risk (Després, Circulation 2012). Waist > 102 cm in men and > 88 cm in women is a visceral-fat marker.

6 real causes

• 1. Insulin resistance — high insulin blocks fat release from the visceral depot
• 2. Chronic stress and cortisol
• 3. Alcohol — directly increases visceral fat ("beer belly" isn't only beer)
• 4. Sleep debt < 6 h — raises cortisol and appetite
• 5. Menopause — falling oestrogen shifts fat from hips to belly
• 6. Refined fructose — makes 2–3× more visceral and liver fat than glucose

Which tests to take

• Fasting insulin + glucose (HOMA-IR)
• HbA1c
• Lipids: TG, HDL, LDL, apoB
• Liver enzymes: ALT, AST, γ-GT
• hsCRP
• Cortisol (morning and/or 4× saliva)
• TSH + fT3
• Sex hormones (perimenopausal women)

What actually works

• Cutting carbs — reduces visceral fat 2× more than cutting fat
• Strength training 3×/week — better than cardio for visceral fat (Neeland et al., 2019)
• 8–9 h sleep + cortisol management
• Alcohol under 4 drinks/week
• 8–10 h eating window (16:8 intermittent fasting)