PHOSPHORUS MAGNETIC-RESONANCE SPECTRA AND CHANGES IN BODY-COMPOSITIONDURING WEIGHT-LOSS

Objective: The use of magnetic resonance spectroscopy (MRS) to monitor cellular bioenergetics during weight loss may provide novel insights regarding metabolic functioning. Methods: Changes were noted in 18 sed entary, moderately overweight women following a 7-week program consist ing of a low-fat, 422-428 MJ/day (1010-1025 kcal/day) diet, a progress ive walking program, a vitamin-mineral-fortified, isolated-protein mea l supplement drink and a weekly group meeting. Mitochondrial energy pr oduction and utilization were assessed by measuring the concentrations of inorganic phosphate (Pi) and phosphocreatine (PCr) through magneti c resonance spectroscopy. Anthropometric changes were also monitored. Results: Dietary analysis of subjects' preintervention food records sh owed intakes of numerous vitamins and minerals below 100% of the Recom mended Dietary Allowances (RDA), most commonly for folicacid, vitamin E, magnesium, iron and zinc. Relative to preintervention levels, final measurements showed that all women lost body weight, ranging from 2.6 to 10.0 kg. Body mass index declined in all subjects, from 0.55 to 3. 86 kg/m(2). All subjects lost fat mass, ranging from 0.9 to 10.4 kg. S eventeen of 18 women showed a decline in their percentage of body fat, ranging from 2.3 to 10.1%. Twelve of 18 subjects showed an increase o f 0.1-3.5 kg of fat-free mass, with half of these values increasing by >1.0 kg. No changes from baseline levels were found in the Pi/PCr rat io over 7 weeks under resting, exercise or recovery conditions, sugges ting a preservation in muscle energy function over the course of the s tudy while the subjects were losing fat mass and total body weight. Co nclusions: The possible metabolic advantage associated with a program that employs moderate energy restriction, repletion of vitamin and min eral intakes to RDA levels, and a regular aerobic exercise program is proposed.