The Lipid Energy Model
Last week we looked at two papers about lean mass hyper-responders. This was the term developed by Dave Feldman to describe lean, fit, metabolically healthy people, who exhibited striking increases in cholesterol when adopting a low-carb diet. Dave defined lean mass hyper-responders as people with lipid profiles comprising LDL cholesterol ≥200 mg/dL, HDL cholesterol ≥80 mg/dL, and triglycerides (TG) ≤70 mg/dL (Ref 1). The two papers were by Creighton et al (“Paradox of hypercholesterolaemia in highly trained, keto-adapted athletes”) (Ref 2) and Norwitz et al (“Elevated LDL Cholesterol with a Carbohydrate-Restricted Diet: Evidence for a “Lean Mass Hyper-Responder” Phenotype.”) (Ref 3).
Creighton et al studied 10 low-carb athletes and 10 high-carb athletes. Their main finding was that total cholesterol, LDL-cholesterol and HDL-cholesterol were all significantly higher in the low-carb group (65%, 83% and 60% respectively). Their conclusion was that ultra-endurance athletes showed "unique cholesterol profiles." Creighton et al suggested that there may be a functional purpose to the expansion of the circulating cholesterol pool to meet the demand for lipid transport in ultra keto-adapted athletes.
The Norwitz et al paper was a study of 548 adults who responded to a web survey. Of these, 100 were identified as lean mass hyper-responders i.e., having developed a lipid profile comprising raised LDL-C and HDL-C with low triglycerides. An inverse association was observed between BMI and cholesterol changes on a low-carb diet. i.e., lower BMI was associated with greater cholesterol increases. Lean mass hyper-responders (LMHRs) were found to have normal levels of LDL-C before a low-carb diet, but large increases in LDL-C and HDL-C on a low-carb diet. (Moderate reintroduction of carbohydrate produced a marked decrease in LDL-cholesterol). In some LMHR cases, LDL-C levels may exceed 500 mg/dL (12.93 mmol/L), absent of any genetic (Familial Hypercholesterolemia) type explanation for this.