Carbohydrate, fat and EPK: what an overfeeding experiment can tell us

The experiment

Horton and colleagues (1995) studied 16 men in a randomised crossover trial: two 14-day periods at 50% above maintenance, adding either carbohydrate or fat. Food was provided; whole-room calorimetry assessed expenditure and fuel oxidation.

What changed

Carbohydrate overfeeding increased expenditure and carbohydrate oxidation while suppressing fat oxidation. Fat overfeeding produced little change in expenditure or fat oxidation. The abstract reports storage of 75–85% versus 90–95% of excess energy, respectively. These are energy-storage estimates, not percentages of total intake converted to body fat.

An important qualification

Measured body-fat gains did not differ significantly; small changes approached measurement limits. Calculated daily fat storage converged by day 14. Suppressed fat oxidation helped explain fat accumulation during carbohydrate overfeeding. This short, male-only experiment cannot establish long-term outcomes.

What this means for EPK

Our interpretation is that EPK should be tested alongside dietary composition, rather than treated as a complete account of fuel use. Recording kcal/kg/day gives an exposure measure; it does not specify which fuels the body uses or how expenditure responds.

For EPK–003, this motivates analysis of substrate utilisation alongside energy intake. For EPK–001, it suggests recording carbohydrate, fat and protein as potential modifiers when evaluating the framework. These are proposed applications, not findings from a trial of EPK.

From overfeeding to adequate fuelling

Restoring adequate intake after restriction is a different research question from deliberately exceeding maintenance requirements. The EPK aim of supporting function without persistent under-fuelling needs direct evaluation in that population. This study does not validate a 25 kcal/kg minimum, improved mitochondrial health or a claim that additional energy is always harmless.

A research question worth testing

At the same EPK, does carbohydrate–fat balance affect energy expenditure, functional recovery and body composition in people recovering from prolonged dietary restriction?

A proposed study would hold protein and prescribed energy per kilogram comparable, document prior restriction, and measure actual intake, activity, resting expenditure, body composition and recovery outcomes over time. Equal EPK would not be assumed to mean equal energy sufficiency across participants. Appropriate clinical oversight would be needed for participants at risk during refeeding.

These measurements could test whether dietary composition adds explanatory value beyond EPK alone. Until then, this is a research proposal, not an established dietary prescription.

Related working papers

Read the relevant PDFs: EPK–001 to 007 are the revised version 1.2 papers; EPK–008 to 010 are version 1.0 supplements. Earlier PDFs and DOI records remain on the paper archive.