Energy gap in the aetiology of body weight gain and obesity: A challenging concept with a complex evaluation and pitfalls

The concept of energy gap(s) is useful for understanding the consequence of a small daily, weekly, or monthly positive energy balance and the inconspicuous shift in weight gain ultimately leading to overweight and obesity. Energy gap is a dynamic concept: an initial positive energy gap incurred via an increase in energy intake (or a decrease in physical activity) is not constant, may fade out with time if the initial conditions are maintained, and depends on the 'efficiency' with which the readjustment of the energy imbalance gap occurs with time. The metabolic response to an energy imbalance gap and the magnitude of the energy gap(s) can be estimated by at least two methods, i.e. i) assessment by longitudinal overfeeding studies, imposing (by design) an initial positive energy imbalance gap; ii) retrospective assessment based on epidemiological surveys, whereby the accumulated endogenous energy storage per unit of time is calculated from the change in body weight and body composition. In order to illustrate the difficulty of accurately assessing an energy gap we have used, as an illustrative example, a recent epidemiological study which tracked changes in total energy intake (estimated by gross food availability) and body weight over 3 decades in the US, combined with total energy expenditure prediction from body weight using doubly labelled water data. At the population level, the study attempted to assess the cause of the energy gap purported to be entirely due to increased food intake. Based on an estimate of change in energy intake judged to be more reliable (i.e. in the same study population) and together with calculations of simple energetic indices, our analysis suggests that conclusions about the fundamental causes of obesity development in a population (excess intake vs. low physical activity or both) is clouded by a high level of uncertainty.

Interaction between disinhibition and restraint: Implications for body weight and eating disturbance

An increase in obesity is usually accompanied by an increase in eating disturbances. Susceptibility to these states may arise from different combinations of underlying traits: Three Factor Eating Questionnaire (TFEQ) Restraint and Disinhibition. Two studies were conducted to examine the interaction between these traits; one on-line study (n=351) and one laboratory-based study (n=120). Participants completed a battery of questionnaires and provided self-report measures of body weight and physical activity. A combination of high Disinhibition and high Restraint was associated with a problematic eating behaviour profile (EAT-26), and a higher rate of smoking and alcohol consumption. A combination of high Disinhibition and low Restraint was associated with a higher susceptibility to weight gain and a higher sedentary behaviour. These data show that different combinations of Disinhibition and Restraint are associated with distinct weight and behaviour outcomes.

Weight gain and nutritional intake in obese pregnant women : some clues for intervention

Aim:  Maternal obesity is associated with increased risk of adverse outcomes for mothers and offspring. Strategies to better manage maternal obesity are urgently needed; however, there is little evidence to assist the development of nutrition interventions during antenatal care. The present study aimed to assess maternal weight gain and dietary intakes of overweight and obese women participating in an exercise trial. Results will assist the development of interventions for the management of maternal overweight and obesity. Methods:  Fifty overweight and obese pregnant women receiving antenatal care were recruited and provided dietary and weight data at baseline (12 weeks), 28 weeks, 36 weeks gestation and 6 weeks post-partum. Data collected were compared with current nutritional and weight gain recommendations. Associations used Pearson's correlation coefficient, and ANOVA assessed dietary changes over time, P < 0.05. Results:  Mean prepregnancy body mass index was 34.4 ± 6.6 kg/m2. Gestational weight gain was 10.6 ± 6 kg with a wide range (−4.1 to 23.0 kg). 52% of women gained excessive weight (>11.5 kg for overweight and >9 kg for obese women). Gestational weight gain correlated with post-partum weight retention (P < 0.001). Dietary intakes did not change significantly during pregnancy. No women achieved dietary fat or dietary iron recommendations, only 11% achieved adequate dietary folate, and 38% achieved adequate dietary calcium. Very few women achieved recommended food group servings for pregnancy, with 83% consuming excess servings of non-core foods. Conclusion:  Results provide evidence that early intervention and personalised support for obese pregnant women may help achieve individualised goals for maternal weight gain and dietary adequacy, but this needs to be tested in a clinical setting.

Beneficial effects of exercise : shifting the focus from body weight to other markers of health

Background: Exercise is widely promoted as a method of weight management, while the other health benefits are often ignored. The purpose of this study was to examine whether exercise-induced improvements in health are influenced by changes in body weight. Methods: Fifty-eight sedentary overweight/obese men and women (BMI 31.8 (SD 4.5) kg/m2) participated in a 12-week supervised aerobic exercise intervention (70% heart rate max, five times a week, 500 kcal per session). Body composition, anthropometric parameters, aerobic capacity, blood pressure and acute psychological response to exercise were measured at weeks 0 and 12. Results: The mean reduction in body weight was −3.3 (3.63) kg (p<0.01). However, 26 of the 58 participants failed to attain the predicted weight loss estimated from individuals’ exercise-induced energy expenditure. Their mean weight loss was only −0.9 (1.8) kg (p<0.01). Despite attaining a lower-than-predicted weight reduction, these individuals experienced significant increases in aerobic capacity (6.3 (6.0) ml/kg/min; p<0.01), and a decreased systolic (−6.00 (11.5) mm Hg; p<0.05) and diastolic blood pressure (−3.9 (5.8) mm Hg; p<0.01), waist circumference (−3.7 (2.7) cm; p<0.01) and resting heart rate (−4.8 (8.9) bpm, p<0.001). In addition, these individuals experienced an acute exercise-induced increase in positive mood. Conclusions: These data demonstrate that significant and meaningful health benefits can be achieved even in the presence of lower-than-expected exercise-induced weight loss. A less successful reduction in body weight does not undermine the beneficial effects of aerobic exercise. From a public health perspective, exercise should be encouraged and the emphasis on weight loss reduced.

Overeating as a clue to weight gain: behavioural and physiological interactions in the control of food intake

It has been estimated that 25-50% of people in most affluent societies are either obese or overweight. These disorders are the result of an imbalance between calorific intake and energy expenditure over a prolonged time period. These types of disorders are among the most common health problems in industrialized societies. Addressing these issues and offering new strategies, this thorough new study draws together contributions from interdisciplinary and international group of specialists, includes recent research on genetic influences, features discussions of epidemiological studies and covers both biological and social aspects of obesity.

Effect of the Summer Months on Body Weight and Composition in College Women

BACKGROUND AND OBJECTIVES: College students and young adults are experiencing the greatest increases in rates of obesity, and 20% of college students are classified as obese. The objective of this study was to compare changes and rates of change in body weight and body composition between the freshman academic year and the summer after the freshman year among female college students. METHODS: Participants were recruited early in their freshman year of college to participate in a prospective longitudinal study examining changes in body weight and composition over the college years. Height and weight were measured, and body composition was assessed using dual energy x-ray absorptiometry (DEXA) at the beginning and end of the freshman year. Upon return from the summer for their sophomore year, participants returned to have all measurements repeated. Sixty-nine female participants completed all three visits. RESULTS: Body weight increased 1.3 kg during the academic period and an additional 0.1 kg during the summer period. Body mass index (BMI) increased between the first two visits but did not change between the last two visits. However, percent fat increased at each visit. Fat-free mass significantly increased 0.5 kg over the academic year but decreased by 1.1 kg over the summer (p<0.05). Greater rates of change were detected in percent fat, fat-free mass, and BMI during the summer compared with the academic year (p<0.05). CONCLUSIONS: Differences in body composition between the academic and summer periods may reflect changes in living situations between these periods. Unfavorable changes during the summer suggest the need to promote healthy lifestyles to freshman women before they leave campus for the summer

A systematic review of studies on socioeconomic inequalities in dietary intakes associated with weight gain and overweight/obesity conducted among European adults

This Review examined socioeconomic inequalities in intakes of dietary factors associated with weight gain, overweight/obesity among adults in Europe. Literature searches of studies published between 1990 and 2007 examining socioeconomic position (SEP) and the consumption of energy, fat, fibre, fruit, vegetables, energy-rich drinks and meal patterns were conducted. Forty-seven articles met the inclusion criteria. The direction of associations between SEP and energy intakes were inconsistent. Approximately half the associations examined between SEP and fat intakes showed higher total fat intakes among socioeconomically disadvantaged groups. There was some evidence that these groups consume a diet lower in fibre. The most consistent evidence of dietary inequalities was for fruit and vegetable consumption; lower socioeconomic groups were less likely to consume fruit and vegetables. Differences in energy, fat and fibre intakes (when found) were small-to-moderate in magnitude; however, differences were moderate-to-large for fruit and vegetable intakes. Socioeconomic inequalities in the consumption of energy-rich drinks and meal patterns were relatively under-studied compared with other dietary factors. There were no regional or gender differences in the direction and magnitude of the inequalities in the dietary factors examined. The findings suggest that dietary behaviours may contribute to socioeconomic inequalities in overweight/obesity in Europe. However, there is only consistent evidence that fruit and vegetables may make an important contribution to inequalities in weight status across European regions.

Determinants of rapid weight gain during infancy: Baseline results from the NOURISH randomised controlled trial.

Background: Rapid weight gain in infancy is an important predictor of obesity in later childhood. Our aim was to determine which modifiable variables are associated with rapid weight gain in early life. Methods: Subjects were healthy infants enrolled in NOURISH, a randomised, controlled trial evaluating an intervention to promote positive early feeding practices. This analysis used the birth and baseline data for NOURISH. Birthweight was collected from hospital records and infants were also weighed at baseline assessment when they were aged 4-7 months and before randomisation. Infant feeding practices and demographic variables were collected from the mother using a self administered questionnaire. Rapid weight gain was defined as an increase in weight-for-age Z-score (using WHO standards) above 0.67 SD from birth to baseline assessment, which is interpreted clinically as crossing centile lines on a growth chart. Variables associated with rapid weight gain were evaluated using a multivariable logistic regression model. Results: Complete data were available for 612 infants (88% of the total sample recruited) with a mean (SD) age of 4.3 (1.0) months at baseline assessment. After adjusting for mother's age, smoking in pregnancy, BMI, and education and infant birthweight, age, gender and introduction of solid foods, the only two modifiable factors associated with rapid weight gain to attain statistical significance were formula feeding [OR=1.72 (95%CI 1.01-2.94), P= 0.047] and feeding on schedule [OR=2.29 (95%CI 1.14-4.61), P=0.020]. Male gender and lower birthweight were non-modifiable factors associated with rapid weight gain. Conclusions: This analysis supports the contention that there is an association between formula feeding, feeding to schedule and weight gain in the first months of life. Mechanisms may include the actual content of formula milk (e.g. higher protein intake) or differences in feeding styles, such as feeding to schedule, which increase the risk of overfeeding. Trial Registration: Australian Clinical Trials Registry ACTRN12608000056392

Association between feeding style and weight gain in infants aged 2–7 months

Introduction: Feeding on demand supports an infant’s innate capacity to respond to hunger and satiety cues and may promote later self-regulation of intake. Our aim was to examine whether feeding style (on demand vs to schedule) is associated with weight gain in early life. Methods: Participants were first-time mothers of healthy term infants enrolled NOURISH, an RCT evaluating an intervention to promote positive early feeding practices. Baseline assessment occurred when infants were aged 2-7 months. Infants able to be categorised clearly as feeding on demand or to schedule (mothers self report) were included in the logistic regression analysis. The model was adjusted for gender, breastfeeding and maternal age, education, BMI. Weight gain was defined as a positive difference in baseline minus birthweight z-scores (WHO standards) which indicated tracking above weight percentile. Results: Data from 356 infants with a mean age of 4.4 (SD 1.0) months were available. Of these, 197 (55%) were fed on demand, 42 (12%) were fed on schedule. There was no statistical association between feeding style and weight gain [OR=0.72 (95%CI 0.35-1.46), P=0.36]. Formula fed infants were three times more likely to be fed on schedule and formula feeding was independently associated with increased weight gain [OR=2.02 (95%CI 1.11-3.66), P=0.021]. Conclusion: In this preliminary analysis the association between feeding style and weight gain did not reach statistical significance, however , the effect size may be clinically relevant and future analysis will include the full study sample (N=698).

A prospective study of pregnancy weight gain in Australian women

Background: While weight gain during pregnancy is regarded as important, there has not been a prospective study of measured weight gain in pregnancy in Australia. This study aimed to prospectively evaluate pregnancy-related weight gain against the Institute of Medicine (IOM) recommendations in women receiving antenatal care in a setting where ongoing weight monitoring is not part of routine clinical practice, to describe women's knowledge of weight gain recommendations and to describe the health professional advice received relating to gestational weight gain (GWG). Methods: Pregnant women were recruited ≤20 weeks of gestation (n = 664) from a tertiary obstetric hospital between August 2010 to July 2011 for this prospective observational study. Outcome measures were weight gain from pre-pregnancy to 36 weeks of gestation, weight gain knowledge and health professional advice received. Results: Thirty-six percent of women gained weight according to guidelines. Twenty-six percent gained inadequate weight, and 38% gained excess weight. Fifty-six percent of overweight women gained weight in excess of the IOM guidelines compared with 30% of those who started with a healthy weight (P < 0.001). At 16 weeks, 47% of participants were unsure of the weight gain recommendations for them. Sixty-two percent of women reported that the health professionals caring for them during this pregnancy ‘never’ or ‘rarely’ offered advice about how much weight to gain. Conclusions: The prevalence of inappropriate gestational weight gain in this study was high. The majority of women do not know their recommended weight gain. The advice women received from health professionals relating to healthy weight gain in pregnancy could be improved.

Biology or behavior : which is the strongest contributor to weight gain?

Combating unhealthy weight gain is a major public health and clinical management issue. The extent of research into the etiology and pathophysiology of obesity has produced a wealth of evidence regarding the contributing factors. While aspects of the environment are ‘obesogenic’, weight gain is not inevitable for every individual. What then explains potentially unhealthy weight gain in individuals living within an environment where others remain lean? In this paper we explore the biological compensation that acts in response to a reduced energy intake by reducing energy needs, in order to defend against weight loss. We then examine the evidence that there is only a weak biological compensation to surplus energy supply, and that this allows behavior to drive weight gain. The extent to which biology impacts behavior is also considered.

Estimating the burden of disease attributable to excess body weight in South Africa in 2000

Objective. To estimate the burden of disease attributable to excess body weight using the body mass index (BMI), by age and sex, in South Africa in 2000. Design. World Health Organization comparative risk assessment (CRA) methodology was followed. Re-analysis of the 1998 South Africa Demographic and Health Survey data provided mean BMI estimates by age and sex. Populationattributable fractions were calculated and applied to revised burden of disease estimates. Monte Carlo simulation-modelling techniques were used for the uncertainty analysis. Setting. South Africa. Subjects. Adults 30 years of age. Outcome measures. Deaths and disability-adjusted life years (DALYs) from ischaemic heart disease, ischaemic stroke, hypertensive disease, osteoarthritis, type 2 diabetes mellitus, and selected cancers. Results. Overall, 87% of type 2 diabetes, 68% of hypertensive disease, 61% of endometrial cancer, 45% of ischaemic stroke, 38% of ischaemic heart disease, 31% of kidney cancer, 24% of osteoarthritis, 17% of colon cancer, and 13% of postmenopausal breast cancer were attributable to a BMI 21 kg/m2. Excess body weight is estimated to have caused 36 504 deaths (95% uncertainty interval 31 018 - 38 637) or 7% (95% uncertainty interval 6.0 - 7.4%) of all deaths in 2000, and 462 338 DALYs (95% uncertainty interval 396 512 - 478 847) or 2.9% of all DALYs (95% uncertainty interval 2.4 - 3.0%). The burden in females was approximately double that in males. Conclusions. This study shows the importance of recognising excess body weight as a major risk to health, particularly among females, highlighting the need to develop, implement and evaluate comprehensive interventions to achieve lasting change in the determinants and impact of excess body weight.

What determines weight loss behaviour and body weight satisfaction in Australia? Evidence from the HILDA survey

This thesis undertakes an empirical investigation to identify factors that influence the decision to undertake weight loss behaviour using the nationally representative HILDA dataset. Although many factors influenced the decision, the findings suggested that body weight satisfaction was the greatest determinant of weight loss dieting. This thesis therefore conducted a further empirical study to analyse the determinants of body weight satisfaction. A rank-hypothesis was found to better predict variation in body weight satisfaction levels than the absolute value of the individual's Body Mass Index (BMI) or the relative-norm hypothesis, which are commonly reported in the literature.