Lean Mass Hyper-Responders (LMHR)
Some lean, metabolically healthy individuals on low-carb diets develop dramatically elevated LDL cholesterol alongside excellent HDL and triglyceride levels. This unique "LMHR" phenotype challenges conventional lipid thinking and is the subject of ongoing research.
Who is this for?
- •Low-carb or keto dieters with elevated LDL
- •Lean, active individuals with surprising lipid results
- •Those questioning conventional cholesterol advice
- •Healthcare providers encountering LMHR patients
The Unique Triad
Unlike typical high-LDL patterns (which come with low HDL and high triglycerides), LMHR shows the opposite: high HDL and very low triglycerides. This reversed pattern suggests a fundamentally different metabolic context.
What is LMHR?
LMHR (Lean Mass Hyper-Responder) is a term coined by researcher Dave Feldman to describe a specific lipid phenotype observed in some people following low-carbohydrate diets. It's characterized by three simultaneous findings:
All three criteria must be present for the LMHR classification.
This triad is metabolically unusual—in the general population, high LDL typically comes with metabolic dysfunction (low HDL, high TG, insulin resistance). LMHR represents the opposite: high LDL in the context of excellent metabolic health.
Who Develops the LMHR Profile?
Lean & Active
BMI typically < 25, often athletic or very physically active
Low-Carb/Keto
Following ketogenic, carnivore, or very low-carb diet
Metabolically Healthy
Normal blood pressure, blood sugar, and waist circumference
High Energy Demand
Body relies heavily on fat for fuel
LMHR is rare in overweight individuals or those with metabolic dysfunction. The leaner and more active you are on low-carb, the more likely this pattern emerges.
The Lipid Energy Model
A Proposed Hypothesis
Traditional medicine views high LDL as purely pathological. The Lipid Energy Model, proposed by Dave Feldman, offers an alternative explanation for LMHR:
Energy Trafficking
In lean individuals on low-carb, the body uses LDL particles as "energy boats" to transport fat to muscles and organs for fuel.
Demand-Driven
Higher energy demands (exercise, lean mass) require more lipid transport, hence more LDL particles in circulation.
Functional, Not Pathological?
These particles may be functioning normally in energy metabolism, not causing atherosclerosis, because they're being actively used.
Context Matters
The same LDL number may have different cardiovascular implications depending on metabolic context (healthy vs. insulin resistant).
This is a hypothesis under active investigation. It has NOT been proven that LMHR is cardiovascularly benign. Long-term outcome data is not yet available.
Current Research Status
LMHR is an active area of scientific investigation. Key studies include:
Citizen Science Foundation CAC Study
Completed 2024Coronary artery calcium (CAC) scans in LMHR individuals showed higher-than-expected atherosclerosis burden in some participants, prompting more nuanced interpretation of the LMHR phenotype.
Carb Reintroduction Experiments
PublishedAdding 100-150g carbs daily reverses the LMHR lipid profile within weeks, suggesting a metabolic rather than genetic cause.
ApoB and LDL-P Analysis
OngoingExamining whether LMHR individuals have different particle characteristics than typical high-LDL patients.
No long-term cardiovascular outcome studies exist specifically for LMHR. We don't yet definitively know if this pattern is harmless, harmful, or somewhere in between for heart disease risk.
When to Be More or Less Concerned
May Be Less Concerning If:
- ✓Meet full LMHR criteria (all three markers)
- ✓Lean BMI (< 25) with low body fat
- ✓No family history of early heart disease
- ✓CAC score is zero
- ✓Excellent metabolic markers (low insulin, HbA1c, hsCRP)
- ✓TG/HDL ratio is excellent (< 1.0)
- ✓AIP is negative or very low
- ✓Normal blood pressure
More Concerning If:
- ⚠Overweight or have visceral fat
- ⚠Family history of early cardiovascular disease
- ⚠Elevated or increasing CAC score
- ⚠High Lp(a) levels
- ⚠Signs of insulin resistance despite diet
- ⚠Only LDL high without HDL/TG improvement
- ⚠Elevated inflammatory markers (hsCRP > 1)
- ⚠Hypertension or other CV risk factors
What to Discuss with Your Doctor
Get Advanced Testing
- • CAC (Coronary Artery Calcium) score
- • ApoB or LDL-P (particle count)
- • Lp(a) if not yet tested
- • hsCRP for inflammation
- • Fasting insulin and HOMA-IR
Calculate Key Ratios
- • TG/HDL ratio (should be < 1.0 for LMHR)
- • AIP (Atherogenic Index) - should be negative
- • Total Cholesterol / HDL ratio
Consider Full Context
- • Complete metabolic picture
- • Family cardiovascular history
- • How long on low-carb diet
- • Other lifestyle factors
- • Personal risk tolerance
Discuss Options
- • Watchful waiting with serial monitoring
- • Carb reintroduction trial (reverses pattern)
- • Medication (controversial for LMHR)
- • Lifestyle modifications
- • Regular CAC tracking
Key Takeaways
- •LMHR is a specific phenotype: very high LDL + very high HDL + very low triglycerides
- •It primarily affects lean, active, low-carb individuals—not the typical high-LDL population
- •The Lipid Energy Model proposes these particles serve an energy transport function
- •Recent research shows some LMHR individuals do develop atherosclerosis, requiring individual assessment
- •CAC score and ApoB provide important additional context beyond standard lipids
- •This is an active area of research—recommendations may evolve as data accumulates
- •Individual decisions should be made with a knowledgeable healthcare provider
References
Norwitz NG, Soto-Mota A, Feldman D, et al. The Lipid Energy Model: Reimagining Lipoprotein Function in the Context of Carbohydrate-Restricted Diets. Metabolites. 2022;12(5):460 PMID: 35629964
Norwitz NG, Feldman D, Soto-Mota A, et al. Elevated LDL Cholesterol with a Carbohydrate-Restricted Diet: Evidence for a "Lean Mass Hyper-Responder" Phenotype. Curr Dev Nutr. 2022;6(1):nzab144 PMID: 35106434
Budoff MJ, Manubolu VS, Kinninger A, et al. Carbohydrate Restriction-Induced Elevations in LDL-Cholesterol and Atherosclerosis: The KETO Trial. JACC Adv. 2024;3(9):101109 PMID: 39372369
Medical Disclaimer
The LMHR guide provided on Metabolicum is for educational and informational purposes only. It is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.