Loss of total body potassium during rapid weight loss does not depend on the decrease of potassium concentration in muscles. Different methods to evaluate body composition during a low energy diet

Abstract

OBJECTIVE: The aim of the study was to elucidate whether combustion of skeletal muscle glycogen during a very low calorie diet (VLCD) was associated with decreased muscle potassium content. A comparison between different methods was also performed to evaluate body composition during a VLCD and a low calorie diet (LCD). DESIGN: Dietary treatment of obese women by VLCD and LCD. Measurements after 1 and 2 weeks of VLCD and 6 months of LCD. SUBJECTS: Fifteen perimenopausal obese women aged 46.5AE AE1.3 y and 15 of 48.0AE AE0.7 y of age. MEASUREMENTS: Skeletal muscle biopsies under local anaesthesia. Body composition measurements by means of deal-energy X-ray absorptiometry (DEXA), and measurements of total body potassium ( 40 K) and total body nitrogen (TBN). Measurements of electrolytes and glycogen concentration in muscle samples. RESULTS: In the ®rst study (1 week of VLCD) skeletal muscle glycogen decreased (P`0.01), but muscle potassium increased (P`0.01). Muscle sodium decreased (P`0.01), while muscle magnesium was unaltered. Body weight decreased by 2.9AE AE0.5 kg and 40 K decreased. Fat-free mass (FFM) calculated from 40 K and DEXA decreased by 2.7 vs 1.9 kg (P`0.001). Body fat measured with DEXA decreased by 1.1 kg (P`0.01), but not body fat calculated from 40 K. TBN decreased by 0.03AE AE0.01 kg (P`0.05) and FFM calculated from TBN by 2.9AE AE0.5 kg (P`0.002). In the second study, 6 months on the LCD resulted in 17.0AE AE2.0 kg weight reduction and this was mainly due to reduced body fat, 14.0AE AE2.0 kg measured with DEXA and from 40 K (P`0.001). The decrease in FFM was slight. CONCLUSION: One week of VLCD resulted in muscle glycogen depletion but increased muscle potassium content in spite of decreased total body potassium. FFM contributed to the main part of body weight loss during short periods of severe energy restriction, but remained unchanged during long-term dietary treatment. Body fat became mostly responsible for the body weight loss during long-term LCD. Calculations of changes of FFM from 40 K and TBN seem to overestimate the FFM decrease associated with short-term VLCD.

Insufficient Sleep Undermines Dietary Efforts to Reduce Adiposity

“…The fraction of body weight lost as fat during the 8.5-h time-in-bed condition (56%) is consistent with other published short-term observations (14); however, the combination of energy and sleep restriction in overweight adults resulted in a modified state of negative energy balance characterized by decreased loss of fat and considerably increased loss of fat-free body mass (Table 1, Figure 2). Although rodent studies have established that sleep deprivation can have considerable catabolic effects that resemble protein malnutrition (2), so far, the possibility that sleep loss may have a similar negative impact in humans has not received much attention: a single report found that 1–2 nights of total sleep deprivation was accompanied by elevated 24-h urinary nitrogen excretion (15), whereas the effects of reduced sleep duration have not been tested.…”

Concentrations of calcium, copper, iron, magnesium, potassium, sodium and zinc in adult female hair with different body mass indexes in Taiwan

“…Most of the body's potassium ions are stored intracellularly and participate with intracellular sodium ions in maintaining the body's H 2 O at an appropriate acidic-alkaline balance, normal osmotic pressure and normal electrolyte balance (19)(20)(21). Potassium and sodium are thus very important for normal physiological function, especially for H 2 O balance.…”

Value of VLCD supplementation with medium chain triglycerides

“…19 Height, body weight and body mass index Height was measured to the nearest 1.0 cm and weight to the nearest 1.0 kg. The measurements were performed in the morning after an overnight fast.…”