Causes of High Cholesterol and Triglycerides Despite Normal BMI
Elevated cholesterol and triglycerides can occur in individuals with normal BMI due to genetic factors, dietary choices, secondary medical conditions, and certain medications, even when weight appears normal. 1
Primary Causes
Genetic Factors
- Familial hypercholesterolemia: Inherited disorder causing elevated LDL cholesterol levels regardless of weight
- Genetic variations in lipid metabolism: Mutations in genes like LPL, APOC2, APOA5, LMF1, GPIHBP1, and GPD1 can cause hypertriglyceridemia even with normal BMI 1
- Remnant cholesterol accumulation: Genetic factors can lead to increased remnant cholesterol (cholesterol in triglyceride-rich lipoproteins) independent of weight 1
Dietary Factors
- High refined carbohydrate intake: Excessive consumption of sugars and refined carbohydrates can significantly raise triglycerides even without weight gain 1, 2
- Alcohol consumption: Even moderate alcohol intake can substantially increase triglyceride levels in susceptible individuals 3
- Low omega-3 fatty acid intake: Insufficient consumption of fatty fish (recommended twice weekly) 1
- Very low-fat diets: Diets with <15% energy from fat can paradoxically lower HDL and raise triglycerides 1
Secondary Medical Conditions
Endocrine Disorders
- Diabetes mellitus/insulin resistance: Can cause dyslipidemia even in normal-weight individuals 2, 3
- Hypothyroidism: Slows metabolism of lipoproteins, raising both cholesterol and triglycerides 3
- Metabolic syndrome: Can occur in normal-weight individuals ("metabolically obese normal weight") 1, 4
Other Medical Conditions
- Chronic liver disease: Impairs lipid metabolism 3
- Chronic kidney disease: Alters lipid metabolism and clearance 3
- Nephrotic syndrome: Increases hepatic production of lipoproteins 4
Medication-Related Causes
Common Medications That Raise Lipids
- Estrogen therapy: Can cause significant rises in plasma triglycerides, especially in those with genetic predisposition 3
- Thiazide diuretics: Can elevate triglycerides and total cholesterol 3
- Beta-blockers: May adversely affect lipid profiles 3
- Glucocorticoids: Can raise both cholesterol and triglycerides 4
- Retinoids: Used for skin conditions, can significantly raise triglycerides 4
- Antiretroviral therapy: Some HIV medications can cause dyslipidemia 4
Lifestyle Factors
- Physical inactivity: Sedentary lifestyle contributes to dyslipidemia even with normal BMI 5
- Hidden visceral adiposity: Normal BMI but high visceral fat ("thin outside, fat inside") 1
Evaluation Approach
Initial Assessment
- Obtain fasting lipid panels: At least two measurements, preferably 2 weeks apart 2
- Screen for secondary causes:
- Liver function tests (including GGT)
- Thyroid function tests
- Fasting glucose or HbA1c
- Renal function tests
- Medication review
Risk Stratification
- Calculate 10-year atherosclerotic cardiovascular disease risk
- Evaluate for metabolic syndrome components despite normal BMI
- Assess for family history of premature cardiovascular disease
Treatment Considerations
Lifestyle Modifications
- Dietary changes: Reduce refined carbohydrates, increase soluble fiber (>10g/day), consume fatty fish twice weekly 1, 2
- Physical activity: 150 minutes/week of moderate-intensity activity can reduce triglycerides by approximately 20% 2
- Alcohol limitation: Reduce or eliminate alcohol consumption 3
Pharmacological Options
- Statins: First-line for elevated LDL cholesterol with cardiovascular risk 2
- Fibrates: Consider for persistent hypertriglyceridemia (e.g., fenofibrate 54-160 mg daily) 2, 3
- Omega-3 fatty acids: Prescription-strength (4g/day) can reduce triglycerides by 25-35% 2
Key Takeaways
- Normal BMI does not exclude metabolic abnormalities that can cause dyslipidemia
- Genetic factors play a significant role in dyslipidemia independent of weight
- Secondary causes should always be investigated before attributing dyslipidemia to lifestyle alone
- Treatment should address underlying causes when possible, alongside appropriate lipid-lowering therapies