Robert C. Klesges

SMOKING, BODY WEIGHT, AND THEIR EFFECTS ON SMOKING BEHAVIOR: A COMPREHENSIVE REVIEW OF THE LITERATURE

This article provides a comprehensive review of the research on smoking and body weight. The relationships between smoking and body weight are evaluated in 70 cross-sectional and longitudinal investigations. The mechanisms responsible for differences in body weight are discussed, the weight-related issues that promote smoking behavior are reviewed, methods for reducing postcessation weight gain are summarized, and future research directions are proposed. A proposed working research model for studying the relationship between smoking, energy balance, and weight gain is offered. It is concluded that smoking and body weight relationships are closely related and pose significant challenges for smoking researchers.

A meta-analysis of the effects of cigarette smoking on bone mineral density

To determine the magnitude and mediators of the association between cigarette smoking and bone mass in the epidemiologic literature we reviewed articles, published abstracts and conference proceedings, identified through MEDLINE, psychological abstracts, conference proceedings, and article bibliographies. We studied cross-sectional and prospective human studies that provided a quantitative measure of bone mass (X-ray, absorptiometry, or computed tomography) as a function of cigarette smoking exposure. Effects were expressed as pooled standardized mean differences for categorical comparisons (e.g. bone mass in current versus nonsmokers), and as pooled correlation coefficients for continuous comparisons (e.g., correlation of bone mass and pack-years of smoking). Effects were derived for combined bone sites (all bone sites pooled within each study) and four specific sites (hip, lumbar spine, forearm, and os calcis), and were examined overall and as a function of subject and methodologic characteristics (gender, age, body weight, menopausal status, health status). Data were pooled across 86 studies, enrolling 40, 753 subjects. Smokers had significantly reduced bone mass compared with nonsmokers (never and former smokers) at all bone sites, averaging a one-tenth standard deviation (SD) deficit for combined sites. Deficits were especially pronounced at the hip, where the bone mass of current smokers was one-third of a SD less than that of never smokers. Overall, effects were greatest in men and in the elderly, and were dosedependent. In prospective studies, smokers had greater rates of bone loss over time compared with nonsmokers. Bone mass differences remained significant after controlling for age and body weight differences between the two groups. Absolute effect sizes at most bone sites were greatest for current smokers compared with never smokers, intermediate for current smokers compared with former smokers, and lowest for former smokers compared with never smokers, suggesting that smoking cessation may have a positive influence on bone mass. Based on these data, it is estimated that smoking increases the lifetime risk of developing a vertebral fracture by 13% in women and 32% in men. At the hip, smoking is estimated to increase lifetime fracture risk by 31% in women and 40% in men. It appears that smoking has an independent, dose-dependent effect on bone loss, which increases fracture risk, and may be partially reversed by smoking cessation. Given the public health implications of smoking on bone health, it is important that this information be incorporated into smoking prevention and cessation efforts

The accuracy of self-reports of physical activity.

This investigation determined the accuracy of self-reports of physical activity compared to observations obtained surreptitiously. Subjects were 44 adults engaged in 1 h of their preferred physical activity while actual activity levels were surreptitiously obtained and compared to immediate self-reported estimates of physical activity. Results indicated that subjects were moderately accurate in recalling their physical activity levels (R = 0.62) but underestimated sedentary activities and overestimated aerobic activities by over 300%. Males overestimated their activity relative to females, and obese subjects underestimated their activity levels compared to normal-weight subjects. Finally, a number of two-way interactions that moderated the accuracy of those subjects engaging in high chronic levels of physical activity were observed.

The relationship between body weight concerns and adolescent smoking.

Although a number of factors have been found to predict smoking status among adolescents, few researchers have examined how belief in smoking as a weight-control strategy may be related to smoking in this high-risk population. With the goal of discovering whether belief in smoking as a weight-control strategy predicted smoking status, the present investigation surveyed 659 Black and White high school students. Analyses showed that among regular smokers, 39% of White female and 12% of White male smokers reported using smoking to control their appetite and weight. In contrast, not a single Black male or female reported using smoking to control appetite and weight. Although belief in smoking as a weight-control strategy did not predict regular smokers versus never smokers, the weight-belief item reliably separated experimental smokers from regular smokers. The survey also revealed that White female restrained eaters were the most likely to actually use smoking as a weight-control strategy.

Effects of obesity, social interactions, and physical environment on physical activity in preschoolers.

Examined demographic, environmental, and parent-child interactional correlates of physical activity in a group of 222 preschoolers. Activity levels were assessed with a system that quantified directly observed physical activity in the natural environment. Using regression-modeling procedures, results revealed a significant relationship between (a) childs relative weight, parental weight status, and percentage of time spent outdoors (environment) and (b) childrens activity levels. Parental obesity was associated with lower levels of physical activity in children, childhood relative weight was associated with slightly higher levels of physical activity, and more outdoor activity was associated with higher activity levels. Parental participation in childrens activities also significantly interacted with levels of parental obesity in predicting activity levels. Those children with a 50% risk for obesity (as defined by both, one, or neither parent being overweight) had small changes in activity across levels of parent-child interaction, whereas those at higher risk for obesity responded with increased activity as parent-child interactions increased. Results are discussed, and the implications of these findings for future intervention efforts are examined.

Who Underreports Dietary Intake in a Dietary Recall? Evidence from the Second National Health and Nutrition Examination Survey.

The present study sought to identify the presence and degree of apparent underreporting of dietary intake in 11,663 participants in the Second National Health and Nutrition Examination Survey (NHANES II). Self-reported dietary intake was compared with estimated basal metabolic rate. Underreporting was based on cutoff limits that identified plausible levels of energy expenditure for adult individuals. Results indicated that up to 31% of adults in this sample may have underreported dietary intake. Those individuals at greatest risk of underreporting were less well educated and heavier. The Sex x Race interaction indicated that for both ethnic categories, women were more likely to underreport than men, but the difference between men and women was greater among Caucasian participants. It is concluded that such factors as reduced energy needs, deliberate falsification, and measurement error inherent in dietary assessment contribute to apparent underreporting, and this occurs in a large percentage of dietary data.

Are weight concerns predictive of smoking cessation ? A prospective analysis

Participants in an 8-session, community based smoking cessation intervention rated whether they would stay quit if they experienced weight gain. The majority reported that they would not relapse to smoking, even after a 20-lb, (9.07-kg) weight gain. Those who were weight concerned were more likely to be female, to weight less and be normal or underweight, and to report chronic dieting. This group was also significantly less likely to be abstinent posttreatment, and at the 1-, 6- and 12-month follow-ups. Individuals presenting for formal smoking cessation interventions may be less weight concerned than the general population of smokers. However, weight-concerned smokers who do present for treatment are less likely to quit smoking. Implications for recruitment and intervention are discussed.

Non-Exercise Activity Thermogenesis. The Crouching Tiger Hidden Dragon of Societal Weight Gain

Non-exercise activity thermogenesis (NEAT) is the energy expenditure of all physical activities other than volitional sporting-like exercise. NEAT includes all the activities that render us vibrant, unique, and independent beings such as working, playing, and dancing. Because people of the same weight have markedly variable activity levels, it is not surprising that NEAT varies substantially between people by up to 2000 kcal per day. Evidence suggests that low NEAT may occur in obesity but in a very specific fashion. Obese individuals appear to exhibit an innate tendency to be seated for 2.5 hours per day more than sedentary lean counterparts. If obese individuals were to adopt the lean “NEAT-o-type,” they could potentially expend an additional 350 kcal per day. Obesity was rare a century ago and the human genotype has not changed over that time. Thus, the obesity epidemic may reflect the emergence of a chair-enticing environment to which those with an innate tendency to sit, did so, and became obese. To reverse obesity, we need to develop individual strategies to promote standing and ambulating time by 2.5 hours per day and also re-engineer our work, school, and home environments to render active living the option of choice.

How much weight gain occurs following smoking cessation ? A comparison of weight gain using both continuous and point prevalence abstinence

Estimates of postcessation weight gain vary widely. This study determined the magnitude of weight gain in a cohort using both point prevalence and continuous abstinence criteria for cessation. Participants were 196 volunteers who participated in a smoking cessation program and who either continuously smoked (n = 118), were continuously abstinent (n = 51), or who were point prevalent abstinent (n = 27) (i.e., quit at the 1-year follow-up visit but not at others). Continuously abstinent participants gained over 13 lbs. (5.90 kg) at 1 year, significantly more than continuously smoking (M = 2.4 lb.) and point prevalent abstinent participants (M = 6.7 lbs., or 3.04 kg). Individual growth curve analysis confirmed that weight gain and the rate of weight gain (pounds per month) were greater among continuously smoking participants and that these effects were independent of gender, baseline weight, smoking and dieting history, age, and education. Results suggest that studies using point prevalence abstinence to estimate postcessation weight gain may be underestimating postcessation weight gain.

The effects of parental influences on children's food intake, physical activity, and relative weight

The current investigation assessed the relationship between observed child mealtime behavior, physical activity, selected parent behaviors, and child relative weight. Subjects were 30 (15 male, 15 female) preschool children varying in age from 22 to 46 months (mean = 30.5 months). Each subject and parents were observed during the dinnertime meal with an observational instrument designed to measure childrens mealtime behaviors and parental influences on child eating. Further, childrens activity levels were assessed for one hour and parental influences on child activity were observed. Results indicated that parental encouragements to eat correlated both with the percent of time the child ate and with child relative weight. Similarly, parental encouragements to be active correlated to extreme levels of child motor activity and negatively to relative weight. Implications of the current study are discussed and the present findings are compared and contrasted with previous research.