The The Carb Cycling Athlete Protocol

What's actually happening

Very active adults who've tried multiple dietary patterns are often underfueling rather than overeating — the failure mode is different. RED-S (relative energy deficiency in sport) describes the syndrome of low energy availability driving hormonal dysregulation, performance decline, and metabolic adaptation in active populations. Sims 2023 (ISSN female-athlete position) addresses RED-S risk, iron status, and protein timing. Phillips 2011 establishes athlete protein at 1.2–2.0 g/kg distributed across 3–4 meals. The Pontzer 2018 constrained-energy model adds nuance: total energy expenditure plateaus despite increases in activity, so cumulative deficit from training plus 'eat less' produces more profound adaptation than for sedentary populations. The lever for this group is often *increasing* food during training cycles, periodizing carbs around training load, and ensuring adequate protein and recovery — not running another deficit.¹Journal of the International Society of Sports Nutrition · 2023Sims ST et al. — International society of sports nutrition position stand: nutritional concerns of the female athlete²Journal of Sports Sciences · 2011Phillips SM, Van Loon LJC — Dietary protein for athletes: from requirements to optimum adaptation³Current Biology · 2016Pontzer H et al. — Constrained total energy expenditure and metabolic adaptation to physical activity in adult humans⁴British Journal of Sports Medicine · 2018Morton RW et al. — A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults⁵Journal of the International Society of Sports Nutrition · 2014Trexler ET, Smith-Ryan AE, Norton LE — Metabolic adaptation to weight loss: implications for the athlete