BMR And Sleep —
Methodology papers are so important.
Basal Metabolic Rate, is measured at complete rest and without physical work ( basal metabolism . This is the energy required for the activity of internal organs and to maintain body temperature. This contributes some 60-70% of Total Energy Expenditure. It is said that during sleep the overall metabolism approximates to the basal metabolic rate. Ganpule et al ( European Journal of Clinical Nutrition : Inter individual variability in sleeping metabolic rate in Japanese subjects. , [ 2007] vol 61, 1256-1261) show that the sleeping metabolic rate has a smaller prediction error than basal metabolic rate.
I wonder what effect the REM ( rapid eye movement phase of sleep has on the measurement?
There were an important series of papers on energy in Proceedings of the Nutrtion Society in 2003.
The first by Westerterp discussed the Impacts of vigorous and non-vigorous activity on daily energy expenditure 2003 Proceedings of the Nutrition Society vol 62, 651-661
Activity intensity is a potential determinant of activity-induced energy expenditure. Tri-axial accelerometery is the most objective measurement technique for the assessment of activity intensity, in combination with doubly-labelled water for the measurement of energy expenditure under free-living conditions. Data on the effects of subject characteristics, including body size and age, and exercise training on the relationship between activity intensity and daily energy-expenditure are reviewed. Average daily metabolic rate and non-basal energy expenditure are positively related to body size. The duration and intensity of physical activities do not need to be equivalent to the energy spent on activity. Obese subjects spend more energy on physical activity but can perform fewer activities, especially high-intensity (weight-bearing) activities, because of their higher body weight. Physical activity generally declines gradually from about 60 years of age onwards. Most subjects > 80 years have an activity level well below the level defined for sedentary middle-aged adults. Spending relatively more time on low-intensity activities has a negative effect on the mean physical activity level. To obtain a higher physical activity level does not necessarily imply high-intensity activities. In an average subject 25 % of the activity-induced energy expenditure may be attributed to high-intensity activities. Exercise training, as a form of high-intensity activity, affects the physical activity level more in younger subjects than in elderly subjects.
The second by Blundell et al discusses Cross talk between physical activity and appetite control: does physical activity stimulate appetite? 2003 Proceedings of the Nutrition Society, vol 62 pp 663-666
Physical activity has the potential to modulate appetite control by improving the sensitivity of the physiological satiety signalling system, by adjusting macronutrient preferences or food choices and by altering the hedonic response to food. There is evidence for all these actions. Concerning the impact of physical activity on energy balance, there exists a belief that physical activity drives up hunger and increases food intake, thereby rendering it futile as a method of weight control. There is, however, no evidence for such an immediate or automatic effect. Short (1-2 d)-term and medium (7-16d)-term studies demonstrate that men and women can tolerate substantial negative energy balances of
Lean Body Mass and Catabolism
The response to stress as happens in severe injury or illness is a catabolic state. This results in loss of lean body mass and a worsening physical state.
It is essential that there is adequate nutritional support with protein and energy during this crisis.
Catabolism results in the release of amino acids which are metabolised to end products including urea. There is also the release of intercellular products including potassium, phosphate and magnesium. Arginine oxidation is reflected in creatinine production.
Carlotti et al in QJMed have looked at whether there is an increased rate of creatinine urinary excretion with the catabolic state in children who had experienced severe trauma. They related this to balances of potassium, phosphate and magnesium to evaluate the benefit of nutritional therapy during this crisis.
They concluded that negative balances of intracellular components (potassium, phosphate and magnesium ) and an increase in rate of creatinine excretion heralded the onset of catabolism Carlotti et al 2008 Indicators of lean body mass catabolism: emphasis On the creatinine excretion rate QJ Med vol 101, 197-205
Women’s weight and body composition is significantly influenced by the female sex-steroid hormones.
Concentrations of these hormones change through the menstrual cycle and influence energy bomeostasis. A review by Davidsea et al (2007 ) reviews the scientific literature on the relationship between hormonal changes across the menstrual cycle and energy balance, and whether these changes influence weight loss in women. In the luteal phase of the menstrual cycle it appears that women’s energy intake and energy expenditure are increased and they experience more frequent cravings for foods, particularly those high in carbohydrate and fat. compared to the than during the follicular phase.
The follicular phase of the menstrual cycle includes menstruation , is the first 14 or so days, with processes leading to ovulation under the control of Follicle Stimulating Hormone and later in this first 14 days oestrogen.
After ovulation the luteal phase lasts for another 14 or so days. The ovum has been expressed into the Fallopian tubes and conception is possible. During this phase Luteinising Hormone and progesterone concentrations increase. There is also a slight increase in body temperature.
These profound hormonal changes are liable to have metabolic and nutritional consequences. Amenorrhoea, absence of periods is a feature of profound weight loss.
The authors of the review suggest that studies are needed to assess the weight loss outcome of tailoring dietary recommendations and the degree of energy restriction to each menstrual phase throughout a weight management program, taking these preliminary findings into account.
A worthy thought . It is interesting that women often accumulate weight during pregnancy and possibly also in their post menopausal period of their lives.