Diane M. Jackson

Uncoupled and surviving: individual mice with high metabolism have greater mitochondrial uncoupling and live longer

Two theories of how energy metabolism should be associated with longevity, both mediated via free‐radical production, make completely contrary predictions. The ‘rate of living‐free‐radical theory’ ( Pearl, 1928 ; Harman, 1956 ; Sohal, 2002 ) suggests a negative association, the ‘uncoupling to survive’ hypothesis ( Brand, 2000 ) suggests the correlation should be positive. Existing empirical data on this issue is contradictory and extremely confused ( Rubner, 1908 ; Yan & Sohal, 2000 ; Ragland & Sohal, 1975 ; Daan et al., 1996 ; Wolf & Schmid‐Hempel, 1989 ]. We sought associations between longevity and individual variations in energy metabolism in a cohort of outbred mice. We found a positive association between metabolic intensity (kJ daily food assimilation expressed as g/body mass) and lifespan, but no relationships of lifespan to body mass, fat mass or lean body mass. Mice in the upper quartile of metabolic intensities had greater resting oxygen consumption by 17% and lived 36% longer than mice in the lowest intensity quartile. Mitochondria isolated from the skeletal muscle of mice in the upper quartile had higher proton conductance than mitochondria from mice from the lowest quartile. The higher conductance was caused by higher levels of endogenous activators of proton leak through the adenine nucleotide translocase and uncoupling protein‐3. Individuals with high metabolism were therefore more uncoupled, had greater resting and total daily energy expenditures and survived longest – supporting the ‘uncoupling to survive’ hypothesis.

Total energy expenditure and physical activity in young Scottish children: mixed longitudinal study

Childhood obesity has been attributed to a decline in total energy expenditure (TEE). We measured TEE, physical activity, and sedentary behaviour in a representative sample of young children from Glasgow, UK, at age 3 years (n=78), and we did a follow-up study at age 5 years (n=72). Mean physical activity level (TEE/resting energy expenditure) was 1.56 (SD 0.39) at age 3 years and 1.61 (0.22) at age 5 years. Median time in sedentary behaviour was 79% of monitored hours at age 3 years (IQR 74-84) and 76% (71-80) at age 5 years. Median time spent in moderate to vigorous physical activity represented only 2% of monitored hours at age 3 years (IQR 1-4) and 4% at age 5 years (2-6). Modern British children establish a sedentary lifestyle at an early age.

Increased television viewing is associated with elevated body fatness but not with lower total energy expenditure in children

BACKGROUND Television (TV) viewing in children is associated with a higher body mass index, but it is unknown whether this reflects body fatness, and, if it does, why. OBJECTIVE The objective was to investigate whether TV viewing is associated with body fatness, physical activity, and total energy expenditure in preschool children. DESIGN Eighty-nine children were recruited into a cross-sectional study. Total daily energy expenditure (TEE) was measured by doubly labeled water, body composition by dual-energy X-ray absorptiometry, and physical activity by accelerometry. RESULTS There was a significant positive association between fat mass (corrected for fat-free body mass) and TV viewing (F = 9.05, P = 0.004). Each extra hour of watching TV was associated with an extra 1 kg of body fat. Children who watched more TV were also significantly less physically active (F = 5.16, P = 0.026). Independent of body composition and sex, children with greater physical activity levels had higher TEE (F = 5.15, P = 0.029); however, physical activity did not mediate the relation between TV viewing and adiposity (P > 0.05). CONCLUSIONS Preschool children who watch more TV are fatter and are less active, and activity influences TEE. However, despite TV viewing being linked to lower physical activity, the relation between TV viewing and fatness is not mediated by physical activity. The results suggest that a relation between TV viewing and fatness is more likely to be due to an effect on food intake.

Effect of a conjugated linoleic acid and omega-3 fatty acid mixture on body composition and adiponectin

This study aimed to determine the effect of supplementation with conjugated linoleic acids (CLAs) plus n‐3 long‐chain polyunsaturated fatty acids (n‐3 LC‐PUFAs) on body composition, adiposity, and hormone levels in young and older, lean and obese men. Young (31.4 ± 3.9 years) lean (BMI, 23.6 ± 1.5 kg/m2; n = 13) and obese (BMI, 32.4 ± 1.9 kg/m2; n = 12) and older (56.5 ± 4.6 years) lean (BMI, 23.6 ± 1.5 kg/m2; n = 20) and obese (BMI, 32.0 ± 1.6 kg/m2; n = 14) men participated in a double‐blind placebo‐controlled, randomized crossover study. Subjects received either 6 g/day control fat or 3 g/day CLA (50:50 cis‐9, trans‐11:trans‐10, cis‐12) and 3 g/day n‐3 LC‐PUFA for 12 weeks with a 12‐week wash‐out period between crossovers. Body composition was assessed by dual‐energy X‐ray absorptiometry. Fasting adiponectin, leptin, glucose, and insulin concentrations were measured and insulin resistance estimated by homeostasis model assessment for insulin resistance (HOMA‐IR). In the younger obese subjects, CLA plus n‐3 LC‐PUFA supplementation compared with control fat did not result in increased abdominal fat and raised both fat‐free mass (2.4%) and adiponectin levels (12%). CLA plus n‐3 LC‐PUFA showed no significant effects on HOMA‐IR in any group but did increase fasting glucose in older obese subjects. In summary, supplementation with CLA plus n‐3 LC‐PUFA prevents increased abdominal fat mass and raises fat‐free mass and adiponectin levels in younger obese individuals without deleteriously affecting insulin sensitivity, whereas these parameters in young and older lean and older obese individuals were unaffected, apart from increased fasting glucose in older obese men.

Validation of energy intake by 24-hour multiple pass recall: comparison with total energy expenditure in children aged 5-7 years.

Accurate measurement of energy intake (EI) is essential in studies of energy balance in all age groups. Reported values for EI can be validated against total energy expenditure (TEE) measured using doubly labelled water (DLW). Our previous work has indicated that the use of the standardized 24 h multiple pass recall (24 h MPR) method produces slight overestimates of EI in pre-school children which are inaccurate at individual level but acceptable at group level. To extend this work, the current study validated EI by 24 h MPR against TEE by DLW in sixty-three (thirty-two boys) school-aged children (median age 6 years). In both boys and girls, reported EI was higher than TEE, although this difference was only significant in the girls (median difference 420 kJ/d, P=0.05). On analysis of agreement between TEE and EI, the group bias was an overestimation of EI by 250 kJ/d with wide limits of agreement (-2880, 2380 kJ/d). EI was over-reported relative to TEE by 7 % and 0.9 % in girls and boys, respectively. The bias in the current study was lower than in our previous study of pre-school children, suggesting that estimates of EI become less inaccurate as children age. However, the current study suggests that the 24 h MPR is inaccurate at the individual level.

Parental feeding style, energy intake and weight status in young Scottish children

Parental feeding style, as measured by the Child Feeding Questionnaire (CFQ), may be an important influence on child feeding behaviour and weight status in early to mid childhood, but more evidence on parental feeding style is required from samples outside the USA. We aimed to use the CFQ in a sample of 117 Scottish children (boys n 53, girls n 64 mean age 4.6 (SD 0.5) years) to: characterise gender differences and changes over time (in forty of the 117 children studied over 2 years); test associations between parental feeding style, free-living energy intake (measured over 3 days using the multiple pass 24-h recall), and weight status (BMI SD score). No dimensions of parental feeding style changed significantly over 2 years in the longitudinal study (P>0.05 in all cases). No aspects of parental feeding style as measured by the CFQ differed significantly between the sexes (P>0.05 in all cases). Parental perceptions of child weight status were generally significantly positively correlated with child weight status as measured by the BMI SD score. In this sample and setting, measures of parental control over child feeding were generally not associated with child energy intake or weight status.

Energy intake by multiple pass 24 h recall and total energy expenditure: a comparison in a representative sample of 3–4-year-olds

The accuracy of the multiple pass 24 h recall for assessment of habitual energy intake in pre-school children is unclear. The primary aim of this study was to assess its accuracy by comparison with measurement of total energy expenditure by doubly-labelled water in a representative sample of forty-one 3-4-year-olds. The recall method was well tolerated by subjects and was administered quickly and easily. However, it produced estimates of energy intake which significantly exceeded measures of total energy expenditure from doubly-labelled water, mean paired difference 660 kJ/d (P<0.01). Agreement between the two methods was poor at the individual level: limits of agreement 660+/-3018 kJ/d. Error and imprecision in both methods contribute to individual differences, but the present study suggests that the multiple pass 24 h recall does not provide accurate estimates of dietary energy intake in individual children.

Total energy expenditure in children with obstructive sleep apnoea syndrome

Childhood obstructive sleep apnoea syndrome (OSAS) acts as a check on growth and nutritional status. An increase in sleeping energy expenditure has been proposed as a possible mechanism, but to date, no studies have determined whether energy requirements (total energy expenditure; TEE) are raised in OSAS. The aim of this study was to test the hypothesis that OSAS is associated with increased TEE. Eleven children (mean+/-SD 5.8+/-2.2 yrs of age) with OSAS confirmed by nocturnal polysomnography were each matched with a pair of healthy controls (n=22) of the same age and sex. TEE was measured using the doubly-labelled water method in all subjects. In 10/11 patients TEE was also measured after adenotonsillectomy and changes in TEE assessed. There was no significant difference in TEE between patients (mean+/-SD 325+/-44 kJ x kg(-1) x day(-1)) and controls (339+/-48 kJ x kg(-1) x day(-1)), nor between patients and age- and sex-specific literature data on TEE, using the doubly-labelled water method. Differences in TEE within patients, before versus after surgery, were minor and not statistically significant. This study does not support the hypothesis that obstructive sleep apnoea syndrome in childhood is associated with increased energy requirements, and suggests that alternative explanations for the effect of this syndrome on growth and energy balance should be sought.

Associations between BMI, social strata and the estimated energy content of foods

OBJECTIVE:Many studies have shown that the prevalence of obesity is greater in lower social classes. The reasons for this effect however are unclear. Since there is also a link between education and social class, and an association between education and prevalence of obesity, one hypothesis is that lack of education about energy contents of foods may contribute to the effects of social class on obesity.SUBJECTS:We tested the hypothesis that knowledge of food energy contents is associated with differences in body mass index (BMI) in a sample of 346 people of both genders, aged between 18 and 45 y, of variable body mass index and drawn from different social strata.RESULTS:Estimates of food energy contents were on average well correlated with the actual energy contents, but individual estimates were very poor in all subpopulations of this sample. We found that subjects of different BMIs did not differentially estimate the energy contents of foods high in carbohydrate, but low in fat and protein (fruit and bread). However, foods that contained high fat contents, independent of the other macronutrients present, were generally perceived to have significantly lower energy contents by obese people than nonobese subjects (although this was not observed for all high-fat foods). Overall, this difference interacted with social class, such that the difference between the BMI groups was exaggerated in the lower social stratum but abolished in the higher social class. Binary logistic regressions revealed that the probability of being obese (BMI>30 kg/m2) in the lower social class group was significantly negatively associated with the estimated food energy content of most high-fat foods. Such an association was not found in the higher social class group. In the lower social class group, overall food knowledge appeared superior in the leaner subject group (BMI<30 kg/m2), but obese subjects were actually better at estimating the energy contents of snacks and alcoholic beverages. The leaner group significantly overestimated the energy contents of these items.CONCLUSION:Differences between individuals in estimates of food energy contents may contribute to the development of obesity in lower social strata. Whether this is driven by a protective effect in lean subjects of overestimating the energy contents of certain foods (snacks and alcoholic beverages) or a susceptibility in the obese because they underestimate the energy contents of other foods is not certain. Knowing which of these alternatives is true is important and may help design public health education programmes directed at these people to help alleviate the obesity epidemic.

Can non-shivering thermogenesis in brown adipose tissue following NA injection be quantified by changes in overlying surface temperatures using infrared thermography?

We aimed to investigate whether infra red thermography (IRT) can be used to measure and quantify non-shivering thermogenesis (NST) in the short-tailed field vole Microtus agrestis, by directly comparing it with a standard method, i.e. metabolic response following Noradrenaline injection (NA). Mean skin surface temperature overlying Brown adipose tissue (BAT) depot was 0.82 degrees C higher than mean surface temperature that did not overly BAT. The difference in temperature increased by 1.26 degrees C after NA was administered. Mean skin surface temperature overlying BAT increased by 0.32 degrees C after NA was administered; however, surface temperature decreased by 1.32 degrees C after saline was administered. Mean skin surface temperature overlying BAT did not change significantly between warm and cold acclimated voles; in contrast metabolic peak following NA injection significantly increased in cold acclimated voles. There was no significant correlation between change in surface temperature after NA injection and metabolic peak following NA injection. The results of this study suggest that IRT is not a sensitive enough method to measure changes in NST capacity in BAT following NA injection, or to detect changes in NST capacity induced by cold acclimation. However, IRT can distinguish between skin surfaces overlying BAT and skin surfaces that do not.