Kong Y. Chen

Amount of Time Spent in Sedentary Behaviors in the United States, 2003–2004

Sedentary behaviors are linked to adverse health outcomes, but the total amount of time spent in these behaviors in the United States has not been objectively quantified. The authors evaluated participants from the 2003-2004 National Health and Nutrition Examination Survey aged >/=6 years who wore an activity monitor for up to 7 days. Among 6,329 participants with at least one 10-hour day of monitor wear, the average monitor-wearing time was 13.9 hours/day (standard deviation, 1.9). Overall, participants spent 54.9% of their monitored time, or 7.7 hours/day, in sedentary behaviors. The most sedentary groups in the United States were older adolescents and adults aged >/=60 years, and they spent about 60% of their waking time in sedentary pursuits. Females were more sedentary than males before age 30 years, but this pattern was reversed after age 60 years. Mexican-American adults were significantly less sedentary than other US adults, and White and Black females were similarly sedentary after age 12 years. These data provide the first objective measure of the amount of time spent in sedentary behavior in the US population and indicate that Americans spend the majority of their time in behaviors that expend very little energy.

Body composition and energy metabolism following Roux-en-Y gastric bypass surgery.

Roux‐en‐Y gastric bypass (RYGB) surgery has become an accepted treatment for excessive obesity. We conducted a longitudinal study to assess regional body composition, muscle proteolysis, and energy expenditure before RYGB, and 6 and 12 months after RYGB. Whole‐body and regional fat mass (FM) and lean mass (LM) were assessed via dual energy X‐ray absorptiometry (DXA), and myofibrillar protein degradation was estimated by urinary 3‐methylhistidine (3‐MeH) in 29 subjects. Energy expenditure and substrate oxidation were also determined using a whole‐room, indirect calorimeter in 12 of these subjects. LM loss constituted 27.8 ± 10.2% of total weight loss achieved 12 months postoperatively, with the majority of LM loss (18 ± 6% of initial LM) occurring in the first 6 months following RYGB. During this period, the trunk region contributed 66% of whole‐body LM loss. LM loss occurred in the first 6 months after RYGB despite decreased muscle protein breakdown, as indicated by a decrease in 3‐MeH concentrations and muscle fractional breakdown rates. Sleep energy expenditure (SEE) decreased from 2,092 ± 342 kcal/d at baseline to 1,495 ± 190 kcal/day at 6 months after RYGB (P < 0.0001). Changes in both LM and FM had an effect on the reduction in SEE (P < 0.001 and P = 0.005, respectively). These studies suggest that loss of LM after RYGB is significant and strategies to maintain LM after surgery should be explored.

Metabolic adaptation following massive weight loss is related to the degree of energy imbalance and changes in circulating leptin

To measure changes in resting metabolic rate (RMR) and body composition in obese subjects following massive weight loss achieved via bariatric surgery or calorie restriction plus vigorous exercise.

Patterns of physical activity in free-living adults in the Southern United States.

Objective: To examine the relationship between the amount and patterns of physical activity (PA), body fatness, and age in a heterogeneous adult population in the free living.Design: Cross-sectional study of the amount of PA over a 1-week period. The amount of body movements during PA (PA counts*103) and time spent on various PA intensity categories were calculated from a triaxial accelerometer and compared with subject characteristics, including body fat from hydrodensitometry.Participants: Adult healthy men (n=48) and women (n=72) were recruited from the Nashville, Tennessee area and their PA was monitored in their free-living environment.Results: The average weekday PA counts (176.5±60.3, P=0.002, r 2=0.294), PA counts day-to-day variability (47.3±32.7, P=0.002, r 2=0.286), daily maximum PA counts (241.9±89.2, P=0.001, r 2=0.327), minute-to-minute variability on weekdays (0.281±0.091, P=0.001, r 2=0.362), and the difference between maximum and minimum daily PA counts (130.6±78.3, P=0.008, r 2=0.243) were significantly and negatively correlated with body fatness. During awake time, both men and women spent 10–12 h on low intensity (1.0–2.9 metabolic equivalents (METs)) PA, approximately 1 h on moderate (3.0–5.9 MET), and less than 10 min on vigorous (>6.0 MET) PA each day. On weekends, men and women spent more time at rest (1 MET), less time on low-intensity PA, and men spent more time on moderate PA than on weekdays.Conclusions: In adults living in the Southern US the amount of free-living PA was negatively correlated with body fatness. Both men and women spent the majority of active time on low and moderate PA. PA patterns on weekends were different than on weekdays and were related to sex and age, but not to body fatness.Sponsorship: National Institutes of Health, US.

Energy expenditure of genuine laughter

Objective:To measure energy expenditure (EE) and heart rate (HR) during genuine laughter.Design:Experimental trial of viewing film clips in four cycles either intended to evoke laughter (humorous −10 min) or unlikely to elicit laughter (not humorous −5 min) under strictly controlled conditions of a whole-room indirect calorimeter equipped with audio recording system.Participants:Forty five adult friend dyads in either same-sex male (n=7), same-sex female (n=21) and mix-sex male-female (n=17); age 18–34 years; body mass index 24.7±4.9 (range 17.9–41.1).Measurements:Energy expenditure in a whole-room indirect calorimeter, HR using Polar HR monitor. Laugh rate, duration and type from digitized audio data using a computerized system and synchronized with HR and EE results.Results:Laughter EE was 0.79±1.30 kJ/min (0.19±0.31 kcal/min) higher than resting EE (P<0.001, 95% confidence interval=0.75–0.88 kJ/min), ranging from –2.52 to 9.67 kJ/min (−0.60–2.31 kcal/min). Heart rate during laughter segments increased above resting by 2.1±3.8 beats/min, ranging from −7.6 to 26.8 beats/min. Laughter EE was correlated with HR (r s=0.250, P<0.01). Both laughter EE and HR were positively correlated with laughter duration (r s=0.282 and 0.337, both P<0.001) and rate (rs=0.256 and 0.298, both P<0.001).Conclusion:Genuine voiced laughter causes a 10–20% increase in EE and HR above resting values, which means that 10–15 min of laughter per day could increase total EE by 40–170 kJ (10–40 kcal).

Plasma leptin association with body composition and energy expenditure in sickle cell disease.

Objective: To examine the association between fasting plasma leptin concentrations and the hypercatabolic state observed in sickle cell disease (SCD). Methods: Plasma leptin concentration and resting energy expenditure (REE) were measured in 37 SCD patients (10 men, 12 boys 14 to 18 years-old, seven women, and eight girls 14 to 18 year-old) and in 37 age, gender and fat mass (FM) matched controls. Body composition was measured hydrostatically, REE by whole room-indirect calorimeter, and plasma leptin using an RIA kit. Results: Plasma leptin concentration and leptin normalized for body fat (ng/dL*kg FM−1) were significantly lower in SCD patients than in non-SCD controls (4.00±3.23 vs. 9.94±14.69, p=0.021 and 0.406±0.260 vs. 0.643±0.561, p=0.024, respectively). A positive linear association between log plasma leptin and FM was observed in both males and females, adjusting for age and SCD status. The strength of this association was greater in females compared with males (slope=0.699 and 0.382 log ng/mL per 10 kg FM, respectively; p=0.013). SCD patients on average demonstrated a higher REE, adjusting for FFM (p<0.0001). Log plasma leptin and FM were not statistically significant predictors of REE after adjustment for FFM and SCD. Conclusions: Once corrected for body composition, mean plasma leptin concentration was significantly lower among female SCD patients than among non-SCD matched controls. Although REE was higher in SCD patients, there is no simple association between leptin and REE in SCD.