Arne Løvø

Description and validation of the ActiReg®: a novel instrument to measure physical activity and energy expenditure

The ActiReg (PreMed AS, Oslo, Norway) system is unique in using combined recordings of body position and motion alone or combined with heart rate (HR) to calculate energy expenditure (EE) and express physical activity (PA). The ActiReg has two pairs of position and motion sensors connected by cables to a battery-operated storage unit fixed to a waist belt. Each pair of sensors was attached by medical tape to the chest and to the front of the right thigh respectively. The collected data were transferred to a personal computer and processed by a dedicated program ActiCalc. Calculation models for EE with and without HR are presented. The models were based on literature values for the energy costs of different activities and therefore require no calibration experiments. The ActiReg system was validated against doubly labelled water (DLW) and indirect calorimetry. The DLW validation demonstrated that neither EE calculated from ActiReg data alone (EEAR) nor from combined ActiReg and HR data (EEAR-HR) were statistically different from DLW results. The EEAR procedure causes some underestimation of EE >11 MJ corresponding to a PA level >2.0. This underestimation is reduced by the EEAR-HR procedure. The objective recording of the time spent in different body positions and at different levels of PA may be useful in studies of PA in different groups and in studies of whether recommendations for PA are being met. The comparative ease of data collection and calculation should make ActiReg a useful instrument to measure habitual PA level and EE.

Validation of energy intake estimated from a food frequency questionnaire: a doubly labelled water study

Objective: The validation of dietary assessment methods is critical in the evaluation of the relation between dietary intake and health. The aim of this study was to assess the validity of a food frequency questionnaire by comparing energy intake with energy expenditure measured with the doubly labelled water method.Design: Total energy expenditure was measured with the doubly labelled water (DLW) method during a 10 day period. Furthermore, the subjects filled in the food frequency questionnaire about 18–35 days after the DLW phase of the study was completed.Subjects: Twenty-one healthy, non-pregnant females volunteered to participate in the study; only 17 subjects completed the study.Results: The group energy intake was on average 10% lower than the energy expenditure, but the difference was not statistically significant. However, there was a wide range in reporting accuracy: seven subjects were identified as acceptable reporters, eight as under-reporters and two were identified as over-reporters. The width of the 95% confidence limits of agreement in a Bland and Altman plot for energy intake and energy expenditure varied from −5 to 3 MJ.Conclusion: The data showed that there was substantial variability in the accuracy of the food frequency questionnaire at the individual level. Furthermore, the results showed that the questionnaire was more accurate for groups than individuals.

Validation of a pre-coded food diary used among 13-year-olds: comparison of energy intake with energy expenditure

OBJECTIVE To validate energy intake (EI) estimated from pre-coded food diaries against energy expenditure (EE) measured with a validated position-and-movement monitor (ActiReg) in groups of 13-year-old Norwegian schoolchildren. DESIGN Two studies were conducted. In study 1 the monitoring period was 4 days; participants recorded their food intake for four consecutive weekdays using food diaries and wore the ActiReg during the same period. In study 2 the monitoring period was 7 days; participants recorded their food intake for four consecutive days but wore the ActiReg for a whole week. SETTINGS Participants were recruited from grade 8 in a school in and one outside Oslo (Norway). SUBJECTS Forty-one and 31 participants from study 1 and 2, respectively, completed the study. RESULTS The group average EI was 34% lower than the measured EE in study 1 and 24% lower in study 2. The width of the 95% confidence limits of agreement in a Bland-Altman plot for EI and EE varied from -0.2 MJ to 8.2 MJ in study 1 and from -2.3 MJ to 6.9 MJ in study 2. The Pearson correlation coefficients between reported energy intake and expenditure were 0.47 (P=0.002) in study 1 and 0.74 (P<0.001) in study 2. CONCLUSION The data showed that there was substantial variability in the accuracy of the food diary at the individual level. Furthermore, the diary underestimated the average energy intake. The ability of the food diary to rank individuals according to energy intake was found to be good in one of the studies and moderate in the other.

Protein metabolism in rats with ventromedial hypothalamic lesions

Abstract The finding that destruction of the ventromedial area of hypothalamus in rats results in obesity has been correlated to the hyperphagia possessed by these animals. Recently, however, obesity has been demonstrated even on restricted food intakes, which indicates that changes in carbohydrate and protein metabolism may have taken place as well. To study the latter, nitrogen balance experiments were combined with carcass analyses. Bilateral lesions in the ventromedial hypothalamic area (VMH) in growing rats are shown to cause increased protein catabolism and/or decreased protein synthesis. Nitrogen balance studies reveal that the lesion affects the protein metabolism within 24 hr. Increased food consumption, due to hyperphagia, renders only a transitory positive effect on protein deposition possible. Carcass analyses, confirming the balance data, also demonstrate an altered lipid metabolism. Animals receiving normal or sub-normal amounts of food accumulate more lipids than their increase in body weight, and, in agreement with this, a loss of body water and protein is found. In animals allowed to overeat, more than 80% of their weight gain is accounted for by lipids. Evidence is reported for a normal protein digestion in lesioned animals, and it is suggested that the increased nitrogen excretion is due to an impaired amino acid utilization.

The Effect of Ventromedial Hypothalamic Lesions on Metabolism and Insulin Secretion in Rats on a Controlled Feeding Regimen

The metabolic effect of ventromedial hypothalamic (VMH) lesions, which are known to cause hyperphagia and obesity, has been studied in rats kept on a controlled light and food regimen. The animals were sacrificed at 4 different times during the second postoperative day. A feeding-induced hypersecretion of insulin was found to the VMH-lesioned animals. It was accompanied by a marked hypoglycemia as compared to the control groups during the feeding period. The glycogen content of liver and diaphragm in the lesioned groups is increased as compared to the controls during the same period. The VMH-lesioned animals showed hypertriglyceridemia both in the fed and fasted state, whereas the postabsorptive plasma levels of free fatty acids and glycerol were decreased. An increased level of urea was observed in all lesioned groups. This is in accordance with the demonstrated protein catabolism which follows VMH lesions.

THE EFFECT OF CARBON DIOXIDE ON THE RESPIRATION OF AVIAN DIVERS (DUCKS).

Abstract 1. 1. The normal respiratory effect of CO2 in avian divers has been studied. Domestic ducks (“white Pekin”) served as subjects. 2. 2. The respiratory minute volume (RMV), tidal volume (TV) and respiratory frequency (RF) were recorded. 3. 3. The RMV almost always increased when the ducks breathed gas mixtures with a high content of CO2. 4. 4. The RMV rose due to an augmentation of TV which more than compensated for the tendency of RF to decrease with increasing CO2-concentrations in the inspired air. 5. 5. These findings confirm the observation by Orr & Watson (1913) and Hiestand & Randall (1941), who found that high concentrations of CO2 in the inspired air cause transient periods of apnoea in the duck. However, they do not support the conclusion that CO2 is a respiratory suppressor in diving birds, for the RMV was not reduced until the CO2-concentrations inhaled were raised well above those found in the lungs of diving ducks (Andersen, 1959).

Increased hepatic triacylglycerol secretion in fasted rats with ventromedial hypothalamic lesions

Adult female rats with lesions in the ventromedial hypothalamic area and sham-operated controls were given Triton WR 1339 intravenously after 24 h without food for measurement of liver triacylglycerol secretion rate. Tritiated water was injected for measurement of lipogenesis in liver, perirenal and subcutaneous adipose tissues in vivo. The experiments were performed on unrestrained animals with a chronically implnted venous heart cannula after 24 h without food. By the use of this technique, anesthesia and handling of the animals during the experiments was avoided. The following differences in the lesioned animals compared to the sham-operated controls were found: relative hypertriglyceridemia. A significant increase of triacylglycerol accumulation in the plasma. Increased incorporation of 3H FROM 3H20 into liver fatty acids. The experiments demonstrate that hepatic lipid synthesis during fasting is greater in the lesioned than in the control animals, but not high enough to account for the increased triacylglycerol secretion. A shift in the hepatic metabolism of fatty acids, leading to greater triacylglycerol formation at the expense of other processes is therefore suggested. The possible role of insulin in these metabolic changes is discussed.

Correlation between altered acetate utilization and hyperphagia in rats with ventromedial hypothalamic lesions

Abstract Incorporation of a tracer dose of acetate-1- 14 C given by intraperitoneal injection into normal and VMH-lesioned rats 2 days after surgery has been studied in vivo. To exclude adaptive metabolic effects due to meal-feeding and hyperphagia, the food intake of the lesioned animals was kept close to normal by using an automated food dispenser. The results show decreased recovery of 14 C activity as 14 CO 2 in the lesioned rats as compared to untreated animals during the first 4 hr after the injection, whereas the 14 C incorporation into body lipids was significantly increased in the lesioned animals. The change in acetate utilization is shown to develop gradually during the first 2–3 days postoperatively. Moreover, the individual retention of 14 C activity from acetate-1- 14 C is correlated to the subsequent gain in body weight during 8 days of ad-lib. feeding. In conclusion, the results clearly demonstrate an altered metabolism in the VMH-lesioned rat, so as to promote accumulation of body fat, even when hyperphagia is prevented. Furthermore, the concept “regulatory obesity” is reexamined in view of the findings presented.

Protein Depletion and Energy Retention in Rats with Ventromedial Hypothalamic Lesions

The catabolic effect of bilateral lesions in the ventromedial are of the hypothalamus (VMH) was studied in nitrogen-balance experiments and compared with the effect of a sham-operation in control animals. A transitory (24 h) increase in urine nitrogen was found in the controls, while in the lesioned animals, a persistent increase was found as long as the animals were fed. Fasting (48 h) eliminated the difference in urea excretion between the groups. Food-dependent effects of the VMH lesion are suggested. The changes in body and organ composition of VMH-lesioned animals, kept for 4 months on a food intake close to normal, were studied. The massive increase of body lipids and marked decrease of body protein and water was primarily due to increased subcutaneous-and abdominal-fat, and reduced skeletal and skin protein. An almost normal composition of the liver and close to normal amounts of protein in the viscera demonstrate that at least some tissues in VMH animals are able to maintain a normal protein content. Hyperphagia as a means to counteract the increased amino acid catabolism and to sustain the lean body mass is discussed.

Protein Metabolism in Rats with Ventromedial Hypothalamic Lesions: Dietary Effects on Nitrogen Retention

The protein metabolism of rats bearing bilateral lesions in the ventromedial area of hypothalamus (VMH) was studied in nitrogen balance experiments employing high protein and high fat diets. The catabolic effect of VMH destruction was to a great extent counterbalanced by increased protein intake. This indicates that increased amino acid catabolism, rather than impaired mechanisms for protein synthesis, is responsible for the poor nitrogen retention of VMH-lesioned rat fed normal amounts of protein. A trend of increasing nitrogen excretion with increasing dietary fat was found when the caloric intake of VMH-lesioned animals was elevated by substitution of dietary carbohydrates with fat. Persistent liponeogenesis in spite of the high fat intake, is suggested as a possible explanation for this observation.