The Physical Activity Guidelines for Americans

Importance

Approximately 80% of US adults and adolescents are insufficiently active. Physical activity fosters normal growth and development and can make people feel, function, and sleep better and reduce risk of many chronic diseases.

Objective

To summarize key guidelines in the Physical Activity Guidelines for Americans, 2nd edition (PAG).

Process and Evidence Synthesis

The 2018 Physical Activity Guidelines Advisory Committee conducted a systematic review of the science supporting physical activity and health. The committee addressed 38 questions and 104 subquestions and graded the evidence based on consistency and quality of the research. Evidence graded as strong or moderate was the basis of the key guidelines. The Department of Health and Human Services (HHS) based the PAG on the 2018 Physical Activity Guidelines Advisory Committee Scientific Report.

Recommendations

The PAG provides information and guidance on the types and amounts of physical activity to improve a variety of health outcomes for multiple population groups. Preschool-aged children (3 through 5 years) should be physically active throughout the day to enhance growth and development. Children and adolescents aged 6 through 17 years should do 60 minutes or more of moderate-to-vigorous physical activity daily. Adults should do at least 150 minutes to 300 minutes a week of moderate-intensity, or 75 minutes to 150 minutes a week of vigorous-intensity aerobic physical activity, or an equivalent combination of moderate- and vigorous-intensity aerobic activity. They should also do muscle-strengthening activities on 2 or more days a week. Older adults should do multicomponent physical activity that includes balance training as well as aerobic and muscle-strengthening activities. Pregnant and postpartum women should do at least 150 minutes of moderate-intensity aerobic activity a week. Adults with chronic conditions or disabilities, who are able, should follow the key guidelines for adults and do both aerobic and muscle-strengthening activities. Recommendations emphasize that moving more and sitting less will benefit nearly everyone. Individuals performing the least physical activity benefit most by even modest increases in moderate-to-vigorous physical activity. Additional benefits occur with more physical activity. Both aerobic and muscle-strengthening physical activity are beneficial.

Conclusions and Relevance

The Physical Activity Guidelines for Americans, 2nd edition, provides information and guidance on the types and amounts of physical activity that provide substantial health benefits. Health professionals and policy makers should facilitate awareness of the guidelines and promote the health benefits of physical activity and support efforts to implement programs, practices, and policies to facilitate increased physical activity and to improve the health of the US population.

Are health care professionals advising obese patients to lose weight?

CONTEXT

Implementation of the National Institutes of Health's 1998 guidelines, which recommended that health care professionals advise obese patients to lose weight, required baseline data for evaluation.

OBJECTIVES

To describe the proportion and characteristics of obese persons advised to lose weight by their health care professional during the previous 12 months and to determine whether the advice was associated with reported attempts to lose weight.

DESIGN

The Behavioral Risk Factor Surveillance System, a random-digit telephone survey conducted in 1996 by state health departments.

SETTING

Population-based sample from 50 states and the District of Columbia.

PARTICIPANTS

A total of 12835 adults, 18 years and older, classified as obese (body mass index > or =30 kg/m2), who had visited their physician for a routine checkup during the previous 12 months.

MAIN OUTCOME MEASURES

Reported advice from a health care professional to lose weight, and reported attempts to lose weight.

RESULTS

Forty-two percent of participants reported that their health care professional advised them to lose weight. Using multivariate logistic regression analysis, we found that the persons who were more likely to receive advice were female, middle aged, had higher levels of education, lived in the northeast, reported poorer perceived health, were more obese, and had diabetes mellitus. Persons who reported receiving advice to lose weight were significantly more likely to report trying to lose weight than those who did not (OR, 2.79; 95% CI, 2.53-3.08).

CONCLUSIONS

Less than half of obese adults report being advised to lose weight by health care professionals. Barriers to counseling need to be identified and addressed.

Reliability and validity of self-reported height and weight among high school students

PURPOSE

To assess the reliability and validity of self-reported height and weight, and variables calculated from these values, in a diverse sample of adolescents.

METHODS

A convenience sample of students (n = 4619) in grades 9 through 12 reported their height and weight on two questionnaires administered approximately 2 weeks apart. Using a standard protocol, a subsample of these students (n = 2032) also were weighed and had their height measured following completion of the first questionnaire.

RESULTS

Self-reported heights at Time 1 and Time 2 were highly correlated, and the mean difference between height at Time 1 and Time 2 was small. Results were similar for self-reported weight at Time 1 and Time 2 and body mass index (BMI) calculated from these values. Although self-reported values of height, weight, and BMI were highly correlated with their measured values, on average, students overreported their height by 2.7 inches and underreported their weight by 3.5 pounds. Resulting BMI values were an average of 2.6 kg/m(2) lower when based on self-reported vs. measured values. The percentages of students classified as "overweight" or "at risk for overweight" were therefore lower when based on self-reported rather than on measured values. White students were more likely than those in other race/ethnic groups to overreport their height, and the tendency to overreport height increased by grade. Female students were more likely than male students to underreport their weight.

CONCLUSIONS

Self-reported height, weight, and BMI calculated from these values were highly reliable but were discrepant from measured height, weight, and BMIs calculated from measured values. BMIs based on self-reported height and weight values therefore underestimate the prevalence of overweight in adolescent populations.

Prevalence of attempting weight loss and strategies for controlling weight

CONTEXT

Overweight and obesity are increasing in the United States. Changes in diet and physical activity are important for weight control.

OBJECTIVES

To examine the prevalence of attempting to lose or to maintain weight and to describe weight control strategies among US adults.

DESIGN

The Behavioral Risk Factor Surveillance System, a random-digit telephone survey conducted in 1996 by state health departments. Setting The 49 states (and the District of Columbia) that participated in the survey.

PARTICIPANTS

Adults aged 18 years and older (N = 107 804).

MAIN OUTCOME MEASURES

Reported current weights and goal weights, prevalence of weight loss or maintenance attempts, and strategies used to control weight (eating fewer calories, eating less fat, or using physical activity) by population subgroup.

RESULTS

The prevalence of attempting to lose and maintain weight was 28.8% and 35.1 % among men and 43.6% and 34.4% among women, respectively. Among those attempting to lose weight, a common strategy was to consume less fat but not fewer calories (34.9% of men and 40.0% of women); only 21.5% of men and 19.4% of women reported using the recommended combination of eating fewer calories and engaging in at least 150 minutes of leisure-time physical activity per week. Among men trying to lose weight, the median weight was 90.4 kg with a goal weight of 81.4 kg. Among women, the median weight was 70.3 kg with a goal weight of 59.0 kg.

CONCLUSIONS

Weight loss and weight maintenance are common concerns for US men and women. Most persons trying to lose weight are not using the recommended combination of reducing calorie intake and engaging in leisure-time physical activity 150 minutes or more per week.

Trends and correlates of class 3 obesity in the United States from 1990 through 2000

CONTEXT

Although the prevalence of obesity has markedly increased among US adults, health risks vary according to the severity of obesity. Persons with class 3 obesity (body mass index [BMI] > or = 40) are at greatest risk, but there is little information about this subgroup.

OBJECTIVE

To examine correlates of class 3 obesity and secular trends.

DESIGN, SETTING, AND PARTICIPANTS

Adults (aged > or = 18 years) in the United States who participated in the Behavioral Risk Factor Surveillance System telephone survey between 1990 (75,600 persons) and 2000 (164,250 persons).

MAIN OUTCOME MEASURE

Body mass index calculated from self-reported weight and height.

RESULTS

The prevalence of class 3 obesity increased from 0.78% (1990) to 2.2% (2000). In 2000, class 3 obesity was highest among black women (6.0%), persons who had not completed high school (3.4%), and persons who are short. During the 11-year period, the median BMI level increased by 1.2 units and the 95th percentile increased by 3.2 units.

CONCLUSION

The prevalence of class 3 obesity is increasing rapidly among adults. Because these extreme BMI levels are associated with the most severe health complications, the incidence of various diseases will increase substantially in the future.

Evidence that oestrogen receptor-alpha plays an important role in the regulation of glucose homeostasis in mice: insulin sensitivity in the liver

AIMS/HYPOTHESIS

We used oestrogen receptor-alpha (ERalpha) knockout (ERKO) and receptor-beta (ERbeta) knockout (BERKO) mice to investigate the mechanism(s) behind the effects of oestrogens on glucose homeostasis.

METHODS

Endogenous glucose production (EGP) was measured in ERKO mice using a euglycaemic-hyperinsulinaemic clamp. Insulin secretion was determined from isolated islets. In isolated muscles, glucose uptake was assayed by using radiolabelled isotopes. Genome-wide expression profiles were analysed by high-density oligonucleotide microarray assay, and the expression of the genes encoding steroyl-CoA desaturase and the Leptin receptor (Scd1 and Lepr, respectively) was confirmed by RT-PCR.

RESULTS

ERKO mice had higher fasting blood glucose, plasma insulin levels and IGT. The plasma leptin level was increased, while the adiponectin concentration was decreased in ERKO mice. Levels of both glucose- and arginine-induced insulin secretion from isolated islets were similar in ERKO and wild-type mice. The euglycaemic-hyperinsulinaemic clamp revealed that suppression of EGP by increased insulin levels was blunted in ERKO mice, which suggests a pronounced hepatic insulin resistance. Microarray analysis revealed that in ERKO mice, the genes involved in hepatic lipid biosynthesis were upregulated, while genes involved in lipid transport were downregulated. Notably, hepatic Lepr expression was decreased in ERKO mice. In vitro studies showed a modest decrease in insulin-mediated glucose uptake in soleus and extensor digitorum longus (EDL) muscles of ERKO mice. BERKO mice demonstrated normal glucose tolerance and insulin release.

CONCLUSIONS/INTERPRETATION

We conclude that oestrogens, acting via ERalpha, regulate glucose homeostasis mainly by modulating hepatic insulin sensitivity, which can be due to the upregulation of lipogenic genes via the suppression of Lepr expression.

Daily steps and all-cause mortality: a meta-analysis of 15 international cohorts

BACKGROUND

Although 10 000 steps per day is widely promoted to have health benefits, there is little evidence to support this recommendation. We aimed to determine the association between number of steps per day and stepping rate with all-cause mortality.

METHODS

In this meta-analysis, we identified studies investigating the effect of daily step count on all-cause mortality in adults (aged ≥18 years), via a previously published systematic review and expert knowledge of the field. We asked participating study investigators to process their participant-level data following a standardised protocol. The primary outcome was all-cause mortality collected from death certificates and country registries. We analysed the dose-response association of steps per day and stepping rate with all-cause mortality. We did Cox proportional hazards regression analyses using study-specific quartiles of steps per day and calculated hazard ratios (HRs) with inverse-variance weighted random effects models.

FINDINGS

We identified 15 studies, of which seven were published and eight were unpublished, with study start dates between 1999 and 2018. The total sample included 47 471 adults, among whom there were 3013 deaths (10·1 per 1000 participant-years) over a median follow-up of 7·1 years ([IQR 4·3-9·9]; total sum of follow-up across studies was 297 837 person-years). Quartile median steps per day were 3553 for quartile 1, 5801 for quartile 2, 7842 for quartile 3, and 10 901 for quartile 4. Compared with the lowest quartile, the adjusted HR for all-cause mortality was 0·60 (95% CI 0·51-0·71) for quartile 2, 0·55 (0·49-0·62) for quartile 3, and 0·47 (0·39-0·57) for quartile 4. Restricted cubic splines showed progressively decreasing risk of mortality among adults aged 60 years and older with increasing number of steps per day until 6000-8000 steps per day and among adults younger than 60 years until 8000-10 000 steps per day. Adjusting for number of steps per day, comparing quartile 1 with quartile 4, the association between higher stepping rates and mortality was attenuated but remained significant for a peak of 30 min (HR 0·67 [95% CI 0·56-0·83]) and a peak of 60 min (0·67 [0·50-0·90]), but not significant for time (min per day) spent walking at 40 steps per min or faster (1·12 [0·96-1·32]) and 100 steps per min or faster (0·86 [0·58-1·28]).

INTERPRETATION

Taking more steps per day was associated with a progressively lower risk of all-cause mortality, up to a level that varied by age. The findings from this meta-analysis can be used to inform step guidelines for public health promotion of physical activity.

FUNDING

US Centers for Disease Control and Prevention.

Vital Signs: Trends in Incidence of Cancers Associated with Overweight and Obesity - United States, 2005-2014

Background

Overweight and obesity are associated with increased risk of at least 13 different types of cancer.

Methods

Data from the United States Cancer Statistics for 2014 were used to assess incidence rates, and data from 2005 to 2014 were used to assess trends for cancers associated with overweight and obesity (adenocarcinoma of the esophagus; cancers of the breast [in postmenopausal women], colon and rectum, endometrium, gallbladder, gastric cardia, kidney, liver, ovary, pancreas, and thyroid; meningioma; and multiple myeloma) by sex, age, race/ethnicity, state, geographic region, and cancer site. Because screening for colorectal cancer can reduce colorectal cancer incidence through detection of precancerous polyps before they become cancerous, trends with and without colorectal cancer were analyzed.

Results

In 2014, approximately 631,000 persons in the United States received a diagnosis of a cancer associated with overweight and obesity, representing 40% of all cancers diagnosed. Overweight- and obesity-related cancer incidence rates were higher among older persons (ages ≥50 years) than younger persons; higher among females than males; and higher among non-Hispanic black and non-Hispanic white adults compared with other groups. Incidence rates for overweight- and obesity-related cancers during 2005–2014 varied by age, cancer site, and state. Excluding colorectal cancer, incidence rates increased significantly among persons aged 20–74 years; decreased among those aged ≥75 years; increased in 32 states; and were stable in 16 states and the District of Columbia.

Conclusions

The burden of overweight- and obesity-related cancer is high in the United States. Incidence rates of overweight- and obesity-related cancers except colorectal cancer have increased in some age groups and states.

Implications for Public Health Practice

The burden of overweight- and obesity-related cancers might be reduced through efforts to prevent and control overweight and obesity. Comprehensive cancer control strategies, including use of evidence-based interventions to promote healthy weight, could help decrease the incidence of these cancers in the United States.

Characterization of signal transduction and glucose transport in skeletal muscle from type 2 diabetic patients

We characterized metabolic and mitogenic signaling pathways in isolated skeletal muscle from well-matched type 2 diabetic and control subjects. Time course studies of the insulin receptor, insulin receptor substrate (IRS)-1/2, and phosphatidylinositol (PI) 3-kinase revealed that signal transduction through this pathway was engaged between 4 and 40 min. Insulin-stimulated (0.6-60 nmol/l) tyrosine phosphorylation of the insulin receptor beta-subunit, mitogen-activated protein (MAP) kinase phosphorylation, and glycogen synthase activity were not altered in type 2 diabetic subjects. In contrast, insulin-stimulated tyrosine phosphorylation of IRS-1 and anti-phosphotyrosine-associated PI 3-kinase activity were reduced 40-55% in type 2 diabetic subjects at high insulin concentrations (2.4 and 60 nmol/l, respectively). Impaired glucose transport activity was noted at all insulin concentrations (0.6-60 nmol/l). Aberrant protein expression cannot account for these insulin-signaling defects because expression of insulin receptor, IRS-1, IRS-2, MAP kinase, or glycogen synthase was similar between type 2 diabetic and control subjects. In skeletal muscle from type 2 diabetic subjects, IRS-1 phosphorylation, PI 3-kinase activity, and glucose transport activity were impaired, whereas insulin receptor tyrosine phosphorylation, MAP kinase phosphorylation, and glycogen synthase activity were normal. Impaired insulin signal transduction in skeletal muscle from type 2 diabetic patients may partly account for reduced insulin-stimulated glucose transport; however, additional defects are likely to play a role.

Attempting to lose weight: specific practices among U.S. adults

BACKGROUND

Americans spend over $33 billion annually on weight-loss products and services. Although weight-control methods are of considerable public health interest, few national data on weight-loss practices are available. This paper examines the prevalence of specific weight-loss practices among U.S. adults trying to lose weight.

METHODS

Data from the 1998 National Health Interview Survey, which was conducted through face-to-face interviews of a nationally representative sample of U.S. adults (n =32,440), were analyzed in 2003.

RESULTS

Twenty-four percent of men and 38% of women were trying to lose weight. Attempting weight loss was less common among normal weight (body mass index [BMI]<25 kg/m(2)) people (6% men, 24% women) than overweight (BMI>/=25 to 30 kg/m(2)) people (28%, 49%) or obese (BMI>/=30 kg/m(2)) people (50%, 58%). Among those trying to lose weight, the most common strategies were eating fewer calories (58% men, 63% women); eating less fat (49%, 56%); and exercising more (54%, 52%). Less frequent strategies were skipping meals (11% men, 9% women); eating food supplements (5%, 6%); joining a weight-loss program (3%, 5%); taking diet pills (2%, 3%); taking water pills or diuretics (1%, 2%); or fasting for >/=24 hours (0.6%, 0.7%). Only one third of all those trying to lose weight reported eating fewer calories and exercising more.

CONCLUSIONS

Increased efforts are needed among all those trying to lose weight to promote effective strategies for weight loss, including the use of calorie reduction and increased physical activity.

Isomer-specific antidiabetic properties of conjugated linoleic acid. Improved glucose tolerance, skeletal muscle insulin action, and UCP-2 gene expression

Conjugated linoleic acid (CLA) isomers have a number of beneficial health effects, as shown in biomedical studies with animal models. Previously, we reported that a mixture of CLA isomers improved glucose tolerance in ZDF rats and activated peroxisome proliferator-activated receptor (PPAR)-gamma response elements in vitro. Here, our aim was to elucidate the effect(s) of specific CLA isomers on whole-body glucose tolerance, insulin action in skeletal muscle, and expression of genes important in glucose and lipid metabolism. ZDF rats were fed either a control diet (CON), one of two CLA supplemented diets (1.5% CLA) containing differing isoforms of CLA (47% c9,t11; 47.9% c10,t12, 50:50; or 91% c9,t11, c9,t11 isomers), or were pair-fed CON diet to match the intake of 50:50. The 50:50 diet reduced adiposity and improved glucose tolerance compared with all other ZDF treatments. Insulin-stimulated glucose transport and glycogen synthase activity in skeletal muscle were improved with 50:50 compared with all other treatments. Neither phosphatidlyinositol 3-kinase activity nor Akt activity in muscle was affected by treatment. Uncoupling protein 2 in muscle and adipose tissue was upregulated by c9,t11 and 50:50 compared with ZDF controls. PPAR-gamma mRNA was downregulated in liver of c9,t11 and pair-fed ZDF rats. Thus, the improved glucose tolerance in 50:50 rats is attributable to, at least in part, improved insulin action in muscle, and CLA effects cannot be explained simply by reduced food intake.

Cigarette smoking and diabetes mellitus: evidence of a positive association from a large prospective cohort study

OBJECTIVE

Only a few prospective studies have examined the relationship between the frequency of cigarette smoking and the incidence of diabetes mellitus. The purpose of this study was to determine whether greater frequency of cigarette smoking accelerated the development of diabetes mellitus, and whether quitting reversed the effect.

METHODS

Data were collected in the Cancer Prevention Study I, a prospective cohort study conducted from 1959 through 1972 by the American Cancer Society where volunteers recruited more than one million acquaintances in 25 US states. From these over one million original participants, 275,190 men and 434,637 women aged > or = 30 years were selected for the primary analysis using predetermined criteria.

RESULTS

As smoking increased, the rate of diabetes increased for both men and women. Among those who smoked > or = 2 packs per day at baseline, men had a 45% higher diabetes rate than men who had never smoked; the comparable increase for women was 74%. Quitting smoking reduced the rate of diabetes to that of non-smokers after 5 years in women and after 10 years in men.

CONCLUSIONS

A dose-response relationship seems likely between smoking and incidence of diabetes. Smokers who quit may derive substantial benefit from doing so. Confirmation of these observations is needed through additional epidemiological and biological research.

Physical activity, food choice, and weight management goals and practices among US college students

INTRODUCTION

Physical activity and a healthy diet have been recommended to help reverse the increasing prevalence of overweight among adolescents and adults in the United States.

METHODS

Data is from the 1995 National College Health Risk Behavior Survey. A representative sample of US undergraduate college students (n = 4609) were analyzed to examine associations of physical activity and food choice with weight management goals and practices.

RESULTS

Based on self-reported height and weight, 35% of students were overweight or obese (body mass index > or = 25.0). Nearly half (46%) of all students reported they were trying to lose weight. Female students were less likely than male students to be overweight, but more likely to be trying to lose weight. Among female and male students, using logistic regression to control for demographics, trying to lose weight was associated with participation in vigorous physical activity and strengthening exercises, and consumption of < or = 2 servings/ day of high-fat foods. Female and male students who reported using exercise to lose weight or to keep from gaining weight were more likely than those who did not to participate in vigorous, strengthening, and moderate physical activity, and were more likely to eat > or = 5 servings/day of fruits and vegetables and < or = 2 servings/day of high-fat foods. Among students who were trying to lose weight, only 54% of females and 41% of males used both exercise and diet for weight control.

CONCLUSION

Colleges should implement programs to increase student awareness of healthy weight management methods and the importance of physical activity combined with a healthy diet.

Colorectal cancer: another complication of diabetes mellitus?

Delayed stool transit and other gastrointestinal abnormalities are commonly observed in persons with diabetes mellitus and are also known to be associated with colorectal cancer. Previous studies of the contribution of diabetes to colorectal cancer incidence and mortality have been limited by small sample sizes and failure to adjust for covariates. With more than 1 million respondents, the 1959-1972 Cancer Prevention Study provided a unique opportunity to explore whether persons with diabetes (n=15,487) were more likely to develop colorectal cancer during a 13-year follow-up period than were persons without diabetes (n=850,946). After adjustment for colorectal cancer risk factors, such as race, educational level, body mass index, smoking, alcohol use, dietary intake, aspirin use, physical activity, and family history of colorectal cancer, the incidence density ratio comparing colorectal cancer in those with diabetes and those without diabetes was 1.30 (95% confidence interval 1.03-1.65) for men and 1.16 (95% confidence interval 0.87-1.53) for women. However, diabetes was not associated with greater case fatality. Future studies should explore the possibility of a cancer-promoting gastrointestinal milieu, including delayed stool transit and elevated fecal bile acid concentrations, associated with hyperglycemia and diabetic neuropathy.

Weight regain in U.S. adults who experienced substantial weight loss, 1999-2002

BACKGROUND

Relatively few studies have focused on who is at risk for weight regain after weight loss and how to prevent it. The objectives of this study were to determine the prevalence and predictors of weight regain in U.S. adults who had experienced substantial weight loss.

METHODS

Data were analyzed from the 1999-2002 National Health and Nutrition Examination Survey (NHANES). This study examined U.S. adults aged 20-84 years who were overweight or obese at their maximum weight (body mass index >/=25) and had experienced substantial weight loss (weighed 10% less than their maximum weight 1 year before they were surveyed) (n=1310).

RESULTS

Compared to their weight 1 year ago, 7.6% had continued to lose weight (>5%), 58.9% had maintained their weight (within 5%), and 33.5% had regained weight (>5%). Factors associated with weight regain (vs weight maintenance or loss) included Mexican American ethnicity (versus non-Hispanic white) (odds ratio [OR]=2.0; 95% confidence interval [CI]=1.3-3.1), losing a greater percentage of maximum weight (>/=20% vs 10% to <15%) (OR=2.8; 95% CI=2.0-4.1), having fewer years since reaching maximum weight (2-5 years vs >10 years) (OR=2.1; 95% CI=1.2-3.7), reporting greater daily screen time (>/=4 hours vs 0-1 hour) (OR=2.0; 95% CI=1.3-3.2), and attempting to control weight (OR=1.8; 95% CI=1.1-3.0). Finally, weight regain was higher in those who were sedentary (OR=1.8; 95% CI=1.0-3.0) or not meeting public health recommendations for physical activity (OR=2.0; 95% CI=1.2-3.5).

CONCLUSIONS

How to achieve the skills necessary for long-term maintenance of weight loss in the context of an obesogenic environment remains a challenge.

Systematic review of the prospective association of daily step counts with risk of mortality, cardiovascular disease, and dysglycemia

BACKGROUND

Daily step counts is an intuitive metric that has demonstrated success in motivating physical activity in adults and may hold potential for future public health physical activity recommendations. This review seeks to clarify the pattern of the associations between daily steps and subsequent all-cause mortality, cardiovascular disease (CVD) morbidity and mortality, and dysglycemia, as well as the number of daily steps needed for health outcomes.

METHODS

A systematic review was conducted to identify prospective studies assessing daily step count measured by pedometer or accelerometer and their associations with all-cause mortality, CVD morbidity or mortality, and dysglycemia (dysglycemia or diabetes incidence, insulin sensitivity, fasting glucose, HbA1c). The search was performed across the Medline, Embase, CINAHL, and the Cochrane Library databases from inception to August 1, 2019. Eligibility criteria included longitudinal design with health outcomes assessed at baseline and subsequent timepoints; defining steps per day as the exposure; reporting all-cause mortality, CVD morbidity or mortality, and/or dysglycemia outcomes; adults ≥18 years old; and non-patient populations.

RESULTS

Seventeen prospective studies involving over 30,000 adults were identified. Five studies reported on all-cause mortality (follow-up time 4-10 years), four on cardiovascular risk or events (6 months to 6 years), and eight on dysglycemia outcomes (3 months to 5 years). For each 1000 daily step count increase at baseline, risk reductions in all-cause mortality (6-36%) and CVD (5-21%) at follow-up were estimated across a subsample of included studies. There was no evidence of significant interaction by age, sex, health conditions or behaviors (e.g., alcohol use, smoking status, diet) among studies that tested for interactions. Studies examining dysglycemia outcomes report inconsistent findings, partially due to heterogeneity across studies of glycemia-related biomarker outcomes, analytic approaches, and sample characteristics.

CONCLUSIONS

Evidence from longitudinal data consistently demonstrated that walking an additional 1000 steps per day can help lower the risk of all-cause mortality, and CVD morbidity and mortality in adults, and that health benefits are present below 10,000 steps per day. However, the shape of the dose-response relation is not yet clear. Data are currently lacking to identify a specific minimum threshold of daily step counts needed to obtain overall health benefit.

Television viewing and its associations with overweight, sedentary lifestyle, and insufficient consumption of fruits and vegetables among US high school students: differences by race, ethnicity, and gender

Television (TV) viewing has been associated with overweight, decreased physical activity, and unhealthy dietary behavior among children and adolescents, and may represent a modifiable cause of childhood obesity. This study examined race, ethnic, and gender-specific differences in these associations among high school students in the United States. The study analyzed data from the 1999 national Youth Risk Behavior Survey, a representative sample (N = 15,349) of US high school students. Logistic regression tested for significant associations. TV viewing on an average school day exceeded 2 hours/day among 43% of students; it was greater among Black (74%) and Hispanic (52%) than White (34%) students. Overall, 11% of students were overweight, 31% of students were sedentary (i.e., did not participate in moderate or vigorous physical activity at recommended levels), and 76% ate less than five servings/day of fruits and vegetables. Watching TV more than 2 hours/day was associated with being overweight, being sedentary, and eating insufficient fruits and vegetables among White females, and with being overweight among Hispanic females. No significant associations were found among Black females. TV viewing was associated with being overweight and eating insufficient fruits and vegetables among White males. No significant associations were found among Hispanic males. Among Black males, TV viewing was associated with greater participation in physical activity. These findings suggest the presence of cultural factors to consider when developing interventions to promote physical activity, healthy eating, and healthy weight through reduced TV viewing among adolescents.

A longitudinal analysis of sugar-sweetened beverage intake in infancy and obesity at 6 years

OBJECTIVE

To examine whether sugar-sweetened beverage (SSB) intake during infancy predicts obesity at age 6 years.

METHODS

We included 1189 children who participated in the Infant Feeding Practices Study II in 2005-2007 and were followed up at 6 years in 2012. Children's weight and height were measured by mothers. Obesity was defined as gender-specific BMI-for-age ≥95th percentile. We used logistic regression to estimate the associations of any SSB intake and age at SSB introduction before 12 months and mean SSB intake during ages 10 to 12 months with obesity at 6 years controlling for baseline characteristics.

RESULTS

The obesity prevalence at 6 years among children who consumed SSBs during infancy was twice as high as that among non-SSB consumers (17.0% vs 8.6%). The adjusted odds of obesity at 6 years was 71% higher for any SSB intake and 92% higher for SSB introduction before 6 months compared with no SSB intake during infancy. Children who consumed SSBs ≥3 times per week during ages 10 to 12 months had twice the odds of obesity compared with those who consumed no SSBs in this period. However, among children who consumed SSBs, the odds of obesity at 6 years did not differ by age at SSB introduction during infancy or by mean weekly SSB intake during ages 10 to 12 months.

CONCLUSIONS

Children who consumed SSBs during infancy had higher odds of obesity at 6 years than non-SSB consumers. SSB consumption during infancy may be a risk factor for obesity in early childhood. Whether unmeasured behaviors contributed to the association is unclear.

C-reactive protein and body mass index in children: findings from the Third National Health and Nutrition Examination Survey, 1988-1994

OBJECTIVES

To examine the relationship between C-reactive protein (CRP) concentration and body mass index (BMI) in children.

STUDY DESIGN

With the use of data from 5305 children aged 6 to 18 years in the Third National Health and Nutrition Examination Survey (1988 to 1994), a cross-sectional health survey, we examined whether CRP concentrations were elevated among overweight children.

RESULTS

Among children whose BMI was below the age- and sex-specific 15th percentile, 6.6% of boys and 10.7% of girls had an elevated CRP concentration (>2.1 mg/L) compared with 24.2% of boys and 31.9% of girls whose BMI was > or =95th percentile. After adjustment was done for age, sex, race or ethnicity, poverty income ratio, high-density lipoprotein cholesterol concentration, white blood cell count, and history of chronic bronchitis, the adjusted odds of having an elevated CRP concentration were 2.20 (95% CI 1.30, 3.75) for children with a BMI of 85th to <95th percentile and 4.92 (95% CI 3.39, 7.15) for children with a BMI of > or =95th percentile compared with children who had a BMI of 15th to <85th percentile. The associations did not differ significantly by age, sex, or race or ethnicity.

CONCLUSIONS

In a large representative sample of US children, CRP concentration was significantly elevated among children with a BMI > or=85th percentile, thus confirming previous findings of this association in children and extending previous research in adults to children. Excess body weight may be associated with a state of chronic low-grade inflammation in children.

Walking trends among U.S. adults: the Behavioral Risk Factor Surveillance System, 1987-2000

OBJECTIVE

To examine trends in walking among adults in 31 states.

METHODS

Trends by sociodemographic strata were analyzed from respondents who participated in the Behavioral Risk Factor Surveillance System (BRFSS).

RESULTS

The prevalence of walking among men increased 3.8% (95% confidence interval [CI]=2.4-5.2), from 26.2% (95% CI=25.1-25.3) in 1987 to 30.1% (95% CI=29.4-30.8) in 2000. In women, walking increased 6.6% (95% CI=5.4-7.8), from 40.4% (95% CI=-39.4-41.1) to 46.9% (95% CI=46.2-47.6) during the same time period. However, the prevalence of walking three times a week for 30 minutes duration remained constant across all years. The largest increases occurred in minority subpopulations: 8.7% (95% CI=3.2-14.2) in Hispanic women, 8.5% (95% CI=4.4-12.6) non-Hispanic black women, and 7.0% (95% CI=2.3-11.7) in non-Hispanic black men. Walking was the most frequently reported activity among adults who met the national recommendations for regular physical activity (defined as five or more times a week for > or =30 minutes per session).

CONCLUSIONS

Given the acceptability of walking across all sociodemographic subgroups, efforts to increase the frequency of walking could markedly increase the percentage of U.S. adults who engage in regular physical activity, a national priority identified in the Healthy People 2010 objectives for the nation.

5-Aminoimidazole-4-carboxamide ribonucleoside treatment improves glucose homeostasis in insulin-resistant diabetic (ob/ob) mice

AIMS/HYPOTHESIS

The 5'AMP-activated protein kinase is an important mediator of muscle contraction-induced glucose transport and a target for pharmacological treatment of Type II (non-insulin-dependent) diabetes mellitus. The 5'AMP-activated protein kinase can be activated by 5-aminoimidazole-4-carboxamide ribonucleoside. We hypothesised that 5-aminoimidazole-4-carboxamide ribonucleoside treatment could restore glucose homeostasis in ob/ob mice.

METHODS

Lean and ob/ob mice were given 5-aminoimidazole-4-carboxamide ribonucleoside (1 mg.g body wt(-1).day(-1) s.c) or 0.9 % NaCl (vehicle) for 1-7 days.

RESULTS

Short-term 5-aminoimidazole-4-carboxamide ribonucleoside treatment normalised glucose concentrations in ob/ob mice within 1 h, with effects persisting over 4 h. After 1 week of daily injections, 5-aminoimidazole-4-carboxamide ribonucleoside treatment corrected hyperglycaemia, improved glucose tolerance, and increased GLUT4 and hexokinase II protein expression in skeletal muscle, but had deleterious effects on plasma non-esterified fatty acids and triglycerides. Treatment with 5-aminoimidazole-4-carboxamide ribonucleoside increased liver glycogen in fasted and fed ob/ob mice and muscle glycogen in fasted, but not fed ob/ob and lean mice. Defects in insulin-stimulated phosphatidylinositol 3-kinase and glucose transport in skeletal muscle from ob/ob mice were not corrected by 5-aminoimidazole-4-carboxamide ribonucleoside treatment. While ex vivo insulin-stimulated glucose transport was reduced in isolated muscle from ob/ob mice, the 5-aminoimidazole-4-carboxamide ribonucleoside stimulated response was normal.

CONCLUSION/INTERPRETATION

The 5-aminoimidazole-4-carboxamide ribonucleoside mediated improvements in glucose homeostasis in ob/ob mice can be explained by effects in skeletal muscle and liver. Due to the apparently deleterious effects of 5-aminoimidazole-4-carboxamide ribonucleoside on the blood lipid profile, strategies to develop tissue-specific and pathway-specific activators of 5'AMP-activated protein kinase should be considered in order to improve glucose homeostasis.

Exercise-induced changes in expression and activity of proteins involved in insulin signal transduction in skeletal muscle: differential effects on insulin-receptor substrates 1 and 2

Level of physical activity is linked to improved glucose homeostasis. We determined whether exercise alters the expression and/or activity of proteins involved in insulin-signal transduction in skeletal muscle. Wistar rats swam 6 h per day for 1 or 5 days. Epitrochlearis muscles were excised 16 h after the last exercise bout, and were incubated with or without insulin (120 nM). Insulin-stimulated glucose transport increased 30% and 50% after 1 and 5 days of exercise, respectively. Glycogen content increased 2- and 4-fold after 1 and 5 days of exercise, with no change in glycogen synthase expression. Protein expression of the glucose transporter GLUT4 and the insulin receptor increased 2-fold after 1 day, with no further change after 5 days of exercise. Insulin-stimulated receptor tyrosine phosphorylation increased 2-fold after 5 days of exercise. Insulin-stimulated tyrosine phosphorylation of insulin-receptor substrate (IRS) 1 and associated phosphatidylinositol (PI) 3-kinase activity increased 2.5- and 3. 5-fold after 1 and 5 days of exercise, despite reduced (50%) IRS-1 protein content after 5 days of exercise. After 1 day of exercise, IRS-2 protein expression increased 2.6-fold and basal and insulin-stimulated IRS-2 associated PI 3-kinase activity increased 2. 8-fold and 9-fold, respectively. In contrast to IRS-1, IRS-2 expression and associated PI 3-kinase activity normalized to sedentary levels after 5 days of exercise. Insulin-stimulated Akt phosphorylation increased 5-fold after 5 days of exercise. In conclusion, increased insulin-stimulated glucose transport after exercise is not limited to increased GLUT4 expression. Exercise leads to increased expression and function of several proteins involved in insulin-signal transduction. Furthermore, the differential response of IRS-1 and IRS-2 to exercise suggests that these molecules have specialized, rather than redundant, roles in insulin signaling in skeletal muscle.

Use of a novel impermeable biotinylated photolabeling reagent to assess insulin- and hypoxia-stimulated cell surface GLUT4 content in skeletal muscle from type 2 diabetic patients

Cell surface GLUT4 levels in skeletal muscle from nine type 2 diabetic subjects and nine healthy control subjects have been assessed by a new technique that involves the use of a biotinylated photo-affinity label. A profound impairment in GLUT4 translocation to the skeletal muscle cell surface in response to insulin was observed in type 2 diabetic patients. Levels of insulin-stimulated cell surface GLUT4 above basal in type 2 diabetic patients were only approximately 10% of those observed in healthy subjects. The magnitude of the defect in GLUT4 translocation in type 2 diabetic patients was greater than that observed for glucose transport activity, which was approximately 50% of that in healthy subjects. Reduced GLUT4 translocation is therefore a major contributor to the impaired glucose transport activity in skeletal muscle from type 2 diabetic subjects. When a marked impairment in GLUT4 translocation occurs, the contribution of other transporters to transport activity becomes apparent. In response to hypoxia, marked reductions in skeletal muscle cell surface GLUT4 levels were also observed in type 2 diabetic patients. Therefore, a defect in a common late stage in signal transduction and/or a direct impairment in the GLUT4 translocation process accounts for reduced glucose transport in type 2 diabetic patients.

U.S. primary care physicians' diet-, physical activity-, and weight-related care of adult patients

BACKGROUND

Overweight and obesity are substantial problems in the U.S., but few national studies exist on primary care physicians' (PCPs') clinical practices regarding overweight and obesity.

PURPOSE

To profile diet, physical activity, and weight control practice patterns of PCPs who treat adults.

METHODS

A nationally representative survey of 1211 PCPs sampled from the American Medical Association's Masterfile was conducted in 2008 and analyzed in 2010. Outcomes included PCPs' assessment, counseling, referral, and follow-up of diet, physical activity, and weight control in adult patients with and without chronic disease and PCPs' use of pharmacologic treatments and surgical referrals for overweight and obesity.

RESULTS

The survey response rate was 64.5%. Half of PCPs (49%) reported recording BMI regularly. Fewer than 50% reported always providing specific guidance on diet, physical activity, or weight control. Regardless of patients' chronic disease status, <10% of PCPs always referred patients for further evaluation/management and <22% reported always systematically tracking patients over time concerning weight or weight-related behaviors. Overall, PCPs were more likely to counsel on physical activity than on diet or weight control (p's<0.05). More than 70% of PCPs reported ever using pharmacologic treatments to treat overweight and 86% had referred for obesity-related surgery.

CONCLUSIONS

PCPs' assessment and behavioral management of overweight and obesity in adults is at a low level relative to the magnitude of the problem in the U.S. Further research is needed to understand barriers to providing care and to improve physician engagement in tracking and managing healthy lifestyles in U.S. adults.