Hypothesis 2: The metabolic adaptation (what is not accounted by a decrease in FM and FFM) is not entirely accounted by reduced organ/tissue size (liver, spleen, kidney, heart and brain) but is accompanied by reduced activities of the sympathetic and thyroid systems. Aim 2: Assess the contribution of organ sizes and activities of the thyroid and sympathetic systems to the metabolic adaptation. Results will be compared to in vivo and in vitro oxidative phosphorylation (Smith, PI).