Bones, hair, and hunger: What long-term caloric restriction reveals for isotope studies?

Bones, hair, and hunger: What long-term caloric restriction reveals for isotope studies?

Controlled feeding experiments are rare but critical for testing the limits of stable isotope applications in palaeodietary research. We conducted a 19-month study on 33 male mice under graded levels of calorie restriction (CR), all maintained on the same diet, to assess impacts on bone collagen and hair keratin δ15N, δ13C, and δ34S values. Collagen δ13C values reflected lipid use under CR, but δ15N values did not show the predicted enrichment, suggesting long-term physiological adaptation. Sulphur isotopes covaried with elemental content, indicating untapped potential for detecting dietary stress. High within-group variability, especially under 30% and 40% CR, points to metabolic flexibility. Finally, unexpected trophic level offset between diet and bone, and hair highlight additional physiological influences, possibly age-related. These results caution against simple interpretations of archaeological isotope data and underscore the need to consider dietary stress and metabolic adaptation.

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