Energy intake (EI) and physical activity energy expenditure (PAEE) are key modifiable determinants of energy balance, traditionally assessed by self-report despite its repeated demonstration of considerable inaccuracies. We argue here that it is time to move from the common view that self-reports of EI and PAEE are imperfect, but nevertheless deserving of use, to a view commensurate with the evidence that self-reports of EI and PAEE are so poor that they are wholly unacceptable for scientific research on EI and PAEE. While new strategies for objectively determining energy balance are in their infancy, it is unacceptable to use decidedly inaccurate instruments, which may misguide health care policies, future research, and clinical judgment. The scientific and medical communities should discontinue reliance on self-reported EI and PAEE. Researchers and sponsors should develop objective measures of energy balance.

Systematic literature search for epidemiological evidence for an association of short sleep with weight gain and eventual development of obesity provided 71 original studies and seven reviews of various subsets of these studies. We have summarized the evidence for such an association with particular emphasis on prospective studies. The studies showed that short sleep duration is consistently associated with development of obesity in children and young adults, but not consistently so in older adults. We have identified critical aspects of the evidence, and assessed the possibility for interpretation of the evidence in terms of causality. We have discussed the requirement of temporal sequence between putative exposure and outcome and the implications of the time lag between them, the problems in adequate measurements of exposure and effects, the possible bidirectional causal effects, the necessary distinction between confounders and mediators, the possible confounding by weight history, and the possibility of common or upstream underlying causes. In conclusion, causal interpretation of the association is hampered by fundamental conceptual and methodological problems. Experimental studies may elucidate mechanisms, but adequate coverage of the entire pathway from sleep curtailment through obesity development is not feasible. Randomized trials are needed to assess the value of targeted interventions.

OBJECTIVE:The aim of this study was to test the hypothesis that specific food intake patterns or changes in food intake patterns were related to future changes in body mass index (BMI). DESIGN: Longitudinal observational study, with clinical and questionnaire examinations at baseline and two follow-up surveys, after 5 and 11 years. SUBJECTS: In all, 3785 men and women attended at baseline, of which 2436 aged 30-60 y attended all three examinations. MEASUREMENTS: A 26-item food frequency questionnaire, standardised measurements of height and weight and a lifestyle questionnaire. Food intake patterns were identified by factor analysis. Regression models including: scores on each factor, BMI, smoking, leisure time physical activity, education, parity, age; and as outcomes: baseline BMI, BMI change between baseline, 5-and 11-y follow-up and obesity at 11-y follow-up, respectively. RESULTS: For men, three factors labelled 'Green', 'Sweet' and 'Traditional', and for women, two factors labelled 'Green' and 'Sweet-Traditional' were identified. Scores on the 'Sweet' and 'Sweet-Traditional' factors were inversely associated with baseline BMI. For men, baseline 'Traditional' factor score and, for women, baseline 'Sweet-Traditional' factor score was inversely associated with subsequent 11-and 5-y BMI change, respectively. Using the three examinations, a more advanced longitudinal model, which included preceding changes in BMI and factor scores, was tested but no significant associations between factor scores, changes in factor scores and subsequent BMI changes or obesity were found. CONCLUSION: In this longitudinal study of a Danish population, food intake factors could not consistently predict changes in BMI or obesity development.

METHOD:We analyzed data pooled from nine studies on the human leptin receptor (LEPR) gene for the association of three alleles (K109R, Q223R and K656N) of LEPR with body mass index (BMI; kg=m 2 ) and waist circumference (WC). A total of 3263 related and unrelated subjects from diverse ethnic backgrounds including African-American, Caucasian, Danish, Finnish, French Canadian and Nigerian were studied. We tested effects of individual alleles, joint effects of alleles at multiple loci, epistatic effects among alleles at different loci, effect modification by age, sex, diabetes and ethnicity, and pleiotropic genotype effects on BMI and WC. RESULTS: We found that none of the effects were significant at the 0.05 level. Heterogeneity tests showed that the variations of the non-significant effects are within the range of sampling variation. CONCLUSION: We conclude that, although certain genotypic effects could be population-specific, there was no statistically compelling evidence that any of the three LEPR alleles is associated with BMI or WC in the overall population.

OBJECTIVE:To examine the association between the habit of eating at night, and the 5-y preceding and 6-y subsequent weight changes in a middle-aged population, with particular focus on the obese. DESIGN: Prospective study with initial examination of the cohort in 1982-83, re-examination in 1987-88 and a third examination in 1992-93. SUBJECTS: The Danish MONICA cohort includes an age-and sex-stratified random sample of the population from the Western part of the Copenhagen County. Out of 2987 subjects participating in 1987-88, a total of 1050 women and 1061 men had been examined in 1982-83, and 1993-94 too. Subjects working night shifts were excluded. MEASUREMENTS: Night eating in 1987-88, 5-y preceding and 6-y subsequent weight change. RESULTS: In total, 9.0% women and 7.4% men reported 'getting up at night to eat'. Obese women with night eating experienced an average 6-y weight gain of 5.2 kg (P ¼ 0.004), whereas only 0.9 kg average weight gain was seen among obese women who did not get up at night to eat. No significant associations were found among all women, or between night eating and the 5-y preceding weight change for women. Night eating and weight change were not associated among men. CONCLUSION: Night eating was not associated with later weight gain, except among already obese women, suggesting that getting up at night to eat may be a contributor to further weight gain among the obese.