Electrocardiographic abnormalities in obese rats fed a commercially available liquid protein diet

Male, obese and non-obese Osborne-Mendel rats were fed a commercially available liquid protein (LP) diet of poor nutritional quality in an amount proportional to that consumed by humans on this diet. Rats fed LP plus vitamins and minerals or a vitamin and mineral mixture only served as control groups. Electrocardiograms (ECG) were recorded weekly until the animals lost 45-50% of their original body weight. ECG's were normal in all groups at the start of the experiment. All rats consuming the LP diet only had arrhythmias. Intractable arrhythmias in the human have been of ventricular origin; in rats in this study various atrial disorders of an inconsistent nature were observed. Serum calcium was low in rats fed the LP diet, but normal in magnesium and potassium concentrations. Calcium, magnesium and potassium were in normal concentrations in cardiac and skeletal muscle, and in bone. Zinc and copper concentrations were low in hearts of rats fed the LP diet. The suggested role of calcium, magnesium and potassium in producing cardiac arrhythmias when subjects consume the liquid protein diet studied here as the sole source of calories is questioned.