Friends and social contexts as unshared environments: a discordant sibling analysis of obesity- and health-related behaviors in young adolescents.

OBJECTIVE: This study examines the contribution of best friends' weight and the peer social context (time spent alone versus with friends) as sources of unshared environment associated with variability in weight and health behaviors among weight-discordant siblings. METHODS: Pairs of same-sex biologic siblings (N=40 pairs; ages 13-17) were originally recruited as part of a study evaluating putative factors contributing to differences in adiposity among weight-discordant siblings. Siblings were asked to bring their best friends to the laboratory and siblings and friends' height and weight were objectively measured. Siblings also completed multi-pass dietary recalls to assess energy intake and sugar sweetened beverage (SSB) consumption. Siblings' physical activity was measured using accelerometry. Experience sampling methodology was used to assess sedentary behaviors/screen time and the number of occasions siblings spent alone and in the presence of friends. Multilevel models were used to estimate the relationships between predictors (best friends' zBMI, time spent alone or with friends) and outcomes (siblings' zBMI and obesity-related health behaviors). RESULTS: Best friends' zBMI was the best predictor of participants' zBMI, even when controlling for child's birth weight. Best friends' weight (zBMI) further predicted participants' SSB intake and time engaged in sedentary behaviors. Being active with friends was positively associated with participants' overall physical activity, whereas spending time alone was negatively associated with accelerometer counts regardless of siblings' adiposity. CONCLUSIONS: A friends' weight and the social context are unshared environmental factors associated with variability in adiposity among biologically-related weight-discordant siblings.

Sensitization of food reinforcement is related to weight status and baseline food reinforcement.

BACKGROUND: Food reinforcement is an empirical index of motivation to obtain food. Higher levels of food reinforcement are associated with increased energy intake and increased body weight. Food reinforcement can vary over repeated food presentations, as people may show reduced reinforcing value if they satiate to repeated reinforcers, or they may show sensitization, or an increase in reinforcing value with repeated presentations. Over the past few years, our laboratory has been studying the impact of repeated administration of large portions of high energy density snack foods on food reinforcement. We have shown in three separate studies that the majority of non-obese individuals become satiated after 2 weeks of the same snack food administration, but that a subset of obese individuals sensitize after this same manipulation. OBJECTIVE: The purpose of the study presented here was to identify predictors of reinforcer satiation or sensitization. SUBJECTS: For the analyses presented here, we combined data sets from three previous studies for a total of 67 adult participants. RESULTS: We found that higher body mass index (BMI) and higher baseline motivation to eat predicted sensitization, and baseline motivation to eat moderated the effects of BMI, such that higher baseline responding for food predicted sensitization in obese individuals, but satiation in non-obese individuals. CONCLUSIONS: These data suggest that repeated exposure to high energy density snack foods may result in sensitization to those foods, with similar effects as drugs of abuse in susceptible individuals, and that an individual's BMI and baseline responding act as predictors of this response.

Home and neighbourhood built environment features in family-based treatment for childhood obesity.

BACKGROUND: Family-based behavioural weight loss treatment (FBT) for childhood obesity helps families develop strategies to facilitate healthy choices in their home and other environments (e.g. home neighbourhood). The current study examines how the home food environment, both pre-FBT and post-FBT, and the neighbourhoods in which families live are associated with child weight and weight-related outcomes in FBT. METHODS: Parent-child dyads (n = 181) completed a 16-session FBT programme and completed home environment, anthropometric and child dietary/activity assessments at pre-FBT and post-FBT. Parents reported on availability of food, electronics and physical activity equipment in the home. The neighbourhood food and recreation environments around each dyad's residence was characterized using existing data within a geographic information system. RESULTS: Families successfully made healthy home environment modifications during FBT. Regression models showed reducing RED (e.g. high-energy-dense and low-nutrient-dense) foods and electronics in the home during FBT had positive effects on child weight and weight-related outcomes. No neighbourhood food or recreation environment variables were significantly related to outcomes, although having a larger density of public recreation spaces was associated with increases in physical activity at the trend-level. CONCLUSIONS: Modifying the home environment, specifically reducing RED foods and electronics, may be particularly important for FBT success.

Nonhomologous recombination in human cells.

Nonhomologous recombination (NHR) is a major pathway for the repair of chromosomal double-strand breaks in the DNA of somatic cells. In this study, a comparison was made between the nonhomologous end joining of transfected adenovirus DNA fragments in vivo and the ability of purified human proteins to catalyze nonhomologous end joining in vitro. Adenovirus DNA fragments were shown to be efficiently joined in human cells regardless of the structure of the ends. Sequence analysis of these junctions revealed that the two participating ends frequently lost nucleotides from the 3' strands at the site of the joint. To examine the biochemical basis of the end joining, nuclear extracts were prepared from a wide variety of mammalian cell lines and tested for their ability to join test plasmid substrates. Efficient ligation of the linear substrate DNA was observed, the in vitro products being similar to the in vivo products with respect to the loss of 3' nucleotides at the junction. Substantial purification of the end-joining activity was carried out with the human immature T-cell-line HPB-ALL. The protein preparation was found to join all types of linear DNA substrates containing heterologous ends with closely equivalent efficiencies. The in vitro system for end joining does not appear to contain any of the three known DNA ligases, on the basis of a number of criteria, and has been termed the NHR ligase. The enriched activity resides in a high-molecular-weight recombination complex that appears to include and require the human homologous pairing protein HPP-1 as well as the NHR ligase. Characterization of the product molecules of the NHR ligase reaction suggests that they are linear oligomers of the monomer substrate joined nonrandomly head-to-head and/or tail-to-tail. The joined ends of the products were found to be modified by a 3' exonuclease prior to ligation, and no circular DNA molecules were detected. These types of products are similar to those required for the breakage-fusion-bridge cycle, a major NHR pathway for chromosome double-strand break repair.

Delay discounting and utility for money or weight loss.

OBJECTIVE: Obesity is related to a bias towards smaller immediate over larger delayed rewards. This bias is typically examined by studying single commodity discounting. However, weight loss often involves choices among multiple commodities. To our knowledge, no research has examined delay discounting of delayed weight loss compared with other commodities. METHODS: We examined single commodity discounting of money and cross commodity discounting of money and weight loss in a sample of 84 adults with obesity or overweight statuses interested in weight loss. The exchange rate between money and weight loss was calculated, and participants completed two delay discounting tasks: money now versus money later and money now versus weight loss later. RESULTS: Participants discounted weight loss more than money (p < 0.001). When participants were divided into those who preferred weight loss (n = 61) versus money (n = 23), those who preferred money over weight loss discounted weight loss even more than individuals that preferred weight loss (p = 0.003). CONCLUSIONS: Greater discounting of weight loss for those who preferred money suggest that idiosyncratic preferences are related to multiple commodity discounting, and greater discounting of weight loss across all participants provide insight on important challenges for weight control.

Effects of a very-low-calorie diet on long-term glycemic control in obese type 2 diabetic subjects.

We tested the hypothesis that the use of a very-low-calorie diet (VLCD) in combination with behavior modification would promote long-term glycemic control in obese type 2 diabetic subjects. Thirty-six diabetic subjects were randomly assigned to a standard behavior therapy program or to a behavior therapy program that included an 8-week period of VLCD. The behavior therapy group consumed a balanced diet of 4200 to 6300 J/d throughout the 20-week program. The VLCD group consumed a balanced diet of 4200 to 6300 J for weeks 1 to 4, followed by a VLCD (1680 J/d of lean meat, fish, and fowl) for weeks 5 to 12. The VLCD group then gradually reintroduced other foods during weeks 13 to 16 and consumed a balanced diet of 4200 to 6300 J/d for weeks 17 to 20. Thirty-three of the 36 subjects completed the 20-week program and the 1-year follow-up. Use of the VLCD produced greater decreases in fasting glucose at the end of the 20-week program and at 1-year follow-up and greater long-term reductions in HbA1. The VLCD group also had greater weight losses at week 20, but weight losses from pretreatment to 1-year follow-up were similar in the two treatment groups. The improved glycemic control with the VLCD appeared to be due to increased insulin secretion, but further research is needed to confirm this.

Long-term effects of modest weight loss in type II diabetic patients.

Since most obese patients with type II diabetes are unable to achieve ideal body weight, this study examined whether more modest weight losses would provide a long-term benefit. Type II diabetic patients (N = 114) were treated in a behavioral weight control program and followed up for one year. Weight loss was significantly correlated with improvements in glycosylated hemoglobin values at posttreatment (r = .55) and one year (r = .51). Patients who lost more than 6.9 kg or had more than 5% reduction in body weight had significant improvements in glycosylated hemoglobin values at one year, while patients losing less weight had nonsignificant changes and those gaining weight had significant worsening. Thus, modest weight loss can have a long-term impact on glycemic control. However, the improvement in glycemic control for a given weight loss was greater initially than at one year, suggesting that energy restriction, in addition to weight loss, may contribute to initial improvement. Neither percent overweight nor diabetes treatment affected weight loss.

Type II diabetic subjects lose less weight than their overweight nondiabetic spouses.

To determine whether diabetic individuals have more difficulty losing weight than nondiabetic individuals, 12 overweight diabetic subjects (6 men, 6 women) and their overweight nondiabetic spouses were treated together in a behavioral weight-control program. Diabetic and nondiabetic subjects did not differ in age, weight, or percent overweight. Weight losses of nondiabetic spouses were significantly greater than those of diabetic patients (13.4 +/- 1.7 vs. 7.5 +/- 1.4 kg; P less than .01). Differences emerged by wk 5 and became greater over the 20-wk program. Nondiabetic subjects reduced their intake significantly more than diabetics, suggesting that differences in dietary adherence were responsible for the differences in weight loss.

Measurement and modification of the accuracy of determinations of urine glucose concentration.

Studies were designed to assess the accuracy of urine glucose testing in a sample of juvenile diabetic subjects, and to determine the effects of a visual discrimination training procedure on the accuracy. In the first study, each of 81 juvenile-diabetic children was presented three prepared glucose solutions and asked to determine the glucose concentration using the 2-Drop Clinitest method. Results showed errors in 54.3% of the judgments, with greatest difficulty occurring with 1-g/dl concentrations. The majority of errors were false negatives. Study II involved similar testing accuracy on a sample of 10 nurses and 2 research technicians, before and after a visual discrimination training procedure. Results showed that the subjects were incorrect on 39% of the trials initially, with a reduction in the error rate to less than 19% after training.

Depressive symptomatology in obese adults with type II diabetes.

This study compared depressive symptomatology in 32 obese subjects with type II (non-insulin-dependent) diabetes (16 men, 16 women) and their obese nondiabetic spouses. All subjects completed the Beck Depression Inventory (BDI) before participation in a behavioral weight-loss program. Diabetic subjects reported significantly more depressive symptomatology than their overweight nondiabetic spouses (10.6 +/- 6.4 vs. 7.5 +/- 6.2, P less than 0.04). Diabetic subjects scored higher than their spouses on 15 of 20 BDI items, with significant differences in feelings of being punished, perceived appearance, and interest in sex. Mean BDI score in the diabetic spouses was similar to that observed in the first 123 diabetic subjects to enter the weight-loss program (BDI 11.2 +/- 6.9). Further studies are needed to determine whether diabetic subjects differ from age-, sex-, and weight-matched nondiabetic individuals in clinical depression and depressive symptomatology.

Compliance to self-monitoring of blood glucose: a marked-item technique compared with self-report.

This study compared subjects' self-reported rates of compliance to self-monitoring of blood glucose (SMBG) with an objective measure based on a "marked-item" technique. We followed 25 obese patients with type II diabetes who were participating in a behavorial weight control program and monitoring their blood glucose with Chemstrips bG (Bio-Dynamics, Inc., Indianapolis, Indiana). Subjects' self-report significantly overestimated actual compliance as assessed by the marked-item technique. Moreover, the self-report measure failed to identify 35-45% of the noncompliant patients. Compliance decreased steadily over the course of the 37-wk program. Accuracy of SMBG was less problematic than compliance; 85% of patients were able to read Chemstrips bG within 20% of actual blood sugar, and the average blood sugar reading obtained from 2 mo of SMBG correlated highly (r = 0.78, P less than 0.01) with HbA1. Our data suggest that objective measures such as the marked-item technique described in this article should be used to assess compliance to SMBG and behavioral strategies to improve compliance should be developed.

Accuracy in estimating fasting blood glucose levels by patients with diabetes.

This study was designed to assess the accuracy with which diabetic patients can estimate their fasting blood sugars (FBS) and to determine whether experience with self-monitoring of blood glucose improves this ability. Twenty patients with type II diabetes who had no experience with self-monitoring of blood glucose were compared with 17 patients who had been monitoring blood sugar regularly for the previous 8 mo. All patients were asked to estimate FBS immediately before it was measured in the laboratory. Patients were very accurate in estimating their FBS; the average error in estimation was 2 mg/dl, and 65% of patients estimated FBS within 20% of actual FBS. However, there was no evidence that experience in self-monitoring of blood glucose improved the accuracy of estimation. Additional studies are needed to determine the types of cues that patients use in estimating blood sugar.

Effects of enhanced conventional therapy on metabolic control in children with insulin-dependent diabetes mellitus.

We implemented a three-phase, 32-wk program to improve both self-regulation of adherence behaviors and insulin delivery in children with diabetes. Twenty children, aged 8-12 yr (mean duration 3.6 yr), enrolled. Phase 1 (wk 1-12) used behavior modification to improve diet, exercise, urine testing, and insulin adjustment, targeting an increased percentage negative urines. Feedback training and parent checks were used to improve reliability; adherence was measured using Clinitest placebos. Phase 2 (wk 13-20) was a stabilization period. Phase 3 (wk 21-32) studied the effect of insulin dose adjustment, comparing once-versus twice-daily shots in 10 pairs of children matched for %GHb. GHb, fasting plasma glucose, and lipids were measured at baseline and at the end of each phase. Results revealed a significant and sustained increase in negative urine tests, but no change in % GHb or FBG. Reliability of and adherence to urine tests were 83% and 76%, respectively. During phase 3, no significant differences were noted between groups receiving once- or twice-daily insulin injections. Thus, behavior modification resulted in increased reliability and adherence to routines, associated with a reliable increase in negative urines. This did not, however, produce changes in other control measures. Furthermore, no differences between those receiving 1 or 2 daily shots were evident.

Analysis of changes in eating behavior and weight loss in type II diabetic patients. Which behaviors to change.

To identify the behavior-change strategies that are most clearly related to weight loss, 106 patients with type II (non-insulin-dependent) diabetes completed the Eating Behavior Inventory (EBI) before and after participating in a behavioral weight-loss program and at 1-yr follow-up. The EBI is a standardized questionnaire that assesses behavioral strategies typically taught in a behavioral weight-loss program. Pretreatment scores on the EBI were not related to weight-loss outcome, but changes on the EBI in the direction of more frequent use of appropriate strategies were related to weight loss at both posttreatment and 1-yr follow-up. Specific strategies related to weight loss at both times were 1) eating foods that help in losing weight, 2) recording foods eaten, 3) refusing food offered by others, and 4) being able to stop eating when appropriate. However, few patients maintained frequent use of these strategies at follow-up. It is concluded that weight-loss programs should focus on the strategies most strongly related to weight loss and try to improve long-term use of these techniques.

Acute effects of nicotine on resting metabolic rate in cigarette smokers.

The acute effects of nicotine on resting metabolic rate (RMR) were examined to identify a mechanism that may help explain the inverse association between smoking and body weight. Multiple administrations of two nicotine doses (moderate [15 micrograms/kg body wt] and low [7.5 micrograms/kg body wt]) and a placebo (0 micrograms) were presented to 18 male smokers via nasal-spray solution on three separate occasions while RMR was assessed by computerized open-circuit indirect calorimetry. Plasma nicotine levels confirmed the reliability of dosing. RMR increases of 6% above base line after both moderate and low doses were significantly greater than the 3% increase after the placebo. Subsequent examination of the effects of smoking a nonnicotine cigarette suggested that the small placebo effect was due to acute metabolic consequences of inhalation. These results confirm that intake of nicotine, isolated from tobacco smoke, significantly increases RMR in humans. However, the results also indicate that non-pharmacological, behavioral aspects of smoking may also contribute to acutely increasing RMR in smokers.

Acute thermogenic effects of nicotine combined with caffeine during light physical activity in male and female smokers.

The thermogenic effects of nicotine and caffeine during physical activity compared with rest were examined in male and female smokers (n = 10 each). During eight sessions, nicotine (15 micrograms/kg) or placebo was given via measured-dose nasal spray intermittently after consumption of decaffeinated coffee with or without added caffeine (5 mg/kg), followed by assessment of energy expenditure by indirect calorimetry while subjects engaged in standardized, low-intensity cycle ergometer riding (activity) or remained at quiet rest. Results indicated significant thermogenic effects of nicotine and caffeine individually, with the combination of nicotine and caffeine producing additive effects. Expenditure attributable to nicotine, caffeine, or their combination was significantly enhanced during activity compared with rest, but only for males and not females. Plasma nicotine concentrations were influenced by activity and caffeine, but these pharmacokinetic changes did not appear to explain the differences in expenditure. These findings suggest a sex difference in thermogenic effects of nicotine and caffeine during casual physical activity and potentially explain some of the apparent individual variability in expenditure due to tobacco smoking.

Metabolic effects of nicotine after consumption of a meal in smokers and nonsmokers.

The thermogenic effect of nicotine intake after calorie consumption was investigated to determine if nicotine influences metabolic response to a calorie challenge. Smokers and nonsmokers (10 males in each group), matched for body weight, age, and physical fitness, each participated in four sessions that involved consuming a liquid calorie load (4.77 kcal/kg body wt) or water, followed by nicotine (15 micrograms/kg body wt) or placebo via nasal spray every 20 min for 2 h. Energy expenditure was significantly increased above baseline resting metabolic rate (RMR) over the 2 h by nicotine alone (6.5% of RMR, p less than 0.01). However, the combined effect of nicotine after calorie load (20.1% of RMR, p less than 0.001) was not significantly greater than the effect of calorie load alone (18.4% of RMR, p less than 0.001). Smokers and nonsmokers did not differ in baseline RMR or in response to nicotine or calorie load. These results confirm the thermogenic effect of nicotine but suggest that the effect of nicotine after calorie consumption is less than additive.

Resting metabolic rate in lean and obese children: relationship to child and parent weight and percent-overweight change.

Two studies were conducted to assess differences in metabolic rate as a function of child weight (study I); and the interaction of child and parent weight (study II). In both studies obese children had higher resting metabolic rates (RMRs) than lean children (p less than 0.05). Child weight accounted for 72 and 78% of the variance in RMR in studies 1 and 2, respectively. Including parental weight did not improve the prediction of RMR. After 6 mo of treatment, obese children decreased percent overweight, whereas lean children showed no change (p less than 0.01). RMR in both groups remained unchanged after 6 mo. These results indicate that the RMR is higher in obese than in lean children, that changes in percent overweight that result from increases in height and no change in weight do not decrease RMR over 6 mo, and parent weight does not improve the prediction of child RMR.

Dietary variety, energy regulation, and obesity.

Increased variety in the food supply may contribute to the development and maintenance of obesity. Thirty-nine studies examining dietary variety, energy intake, and body composition are reviewed. Animal and human studies show that food consumption increases when there is more variety in a meal or diet and that greater dietary variety is associated with increased body weight and fat. A hypothesized mechanism for these findings is sensory-specific satiety, a phenomenon demonstrating greater reductions in hedonic ratings or intake of foods consumed compared with foods not consumed. Nineteen studies documenting change in preference, intake, and hedonic ratings of food after a food has been eaten to satiation in animals and humans are reviewed, and the theory of sensory-specific satiety is examined. The review concludes with the relevance of oral habituation theory as a unifying construct for the effects of variety and sensory-specific satiety, clinical implications of dietary variety and sensory-specific satiety on energy regulation, and suggestions for future research.

Year-long weight loss treatment for obese patients with type II diabetes: does including an intermittent very-low-calorie diet improve outcome?

PURPOSE: To evaluate a year-long behavioral weight control program, used with and without an intermittent very-low-calorie diet (VLCD) in the treatment of type II diabetes mellitus. PATIENTS AND METHODS: Subjects (n = 93) were randomly assigned to 50-week treatment programs that used either a balanced low-calorie diet (LCD) of 1,000 to 1,000 kilocalories (kcal) per day throughout or included 2 12-week periods of a VLCD of 400 to 500 kcal per day alternating with the balanced LCD. Weight, glycemic control, blood pressure, and lipids were assessed at baseline, at the end of the year-long treatment, and at 2-year follow-up. RESULTS: Subjects in the VLCD program lost significantly more weight than did LCD subjects at the end of the 50-week program (14.2 kg versus 10.5 kg; P = 0.057) and remained off diabetes medication longer (P < 0.05). These benefits of the VLCD were due primarily to the first 12 weeks of the diet; the second diet maintained, but did not increase, these effects. Subjects in both groups experienced marked improvements in glycemic control and cardiovascular risk factors over the year-long program, but attendance declined in the latter weeks of treatment and weight was regained. There was also marked recidivism in both groups in the year following treatment. CONCLUSIONS: The intermittent VLCD improved weight loss and glycemic control, but these effects were quite modest and do not appear to justify the clinical use of an intermittent VLCD. Moreover, lengthening treatment to a full year did not prevent relapse. Thus, further research is needed to develop a successful approach to long-term weight control.