Caffeine ingestion is associated with reductions in glucose uptake independent of obesity and type 2 diabetes before and after exercise training

Is breakfast consumption detrimental, unnecessary, or an opportunity for health promotion? A review of cardiometabolic outcomes and functional food choices

Breakfast consumption is generally considered a health-promoting habit for cardiometabolism, particularly with regard to chrononutrition. Glucose uptake is enhanced by proper insulin secretion triggered by the pancreatic clock, averting metabolic dysregulation related to insulin resistance. Breakfast skipping, in turn, is often considered a behaviour detrimental to health, in part due to putative inverse metabolic actions compared to breakfast consumption, such that breakfast skipping may promote circadian desynchrony. However, most ill health concerns about breakfast skipping are inferred from observational research, and recent well-controlled randomized clinical trials have shown benefits of breakfast skipping for cardiovascular risk factors. Accordingly, this review describes the effects of breakfast consumption versus breakfast skipping on cardiovascular risk factors (blood pressure and glycaemic and lipid indices). In addition, the view of breakfast consumption as an opportunity for functional food ingestion is considered to provide further insights into decision-making practice. Collectively, both breakfast consumption and breakfast skipping can be considered viable habits, but they depend on individual preferences, planning, and the specific foods being consumed or omitted. When consumed, breakfast should consist primarily of functional foods typical for this meal (e.g., eggs, dairy products, nuts, fruits, whole grains, coffee, tea, etc.). While breakfast consumption aligns with chrononutrition principles, breakfast skipping can contribute to a calorie deficit over time, which has the potential for widespread cardiometabolic benefits for patients with overweight/obesity. The concepts and practical considerations discussed in the present review may aid health care personnel in personalising breakfast consumption recommendations for diverse patient populations.

Extrapolating the Coffee and Caffeine (1,3,7-Trimethylxanthine) Effects on Exercise and Metabolism-A Concise Review

The consumption of coffee and caffeine (1,3,7-trimethylxanthine) is part of many cultures worldwide. Their properties include serving as a neurostimulant aid, enhancing energy substrate levels, and improving general exercise performance. Both present therapeutic effects that can also be used to control chronic and metabolic diseases due to four mechanisms: adenosine receptor antagonism, increased catecholamine concentrations, a phosphodiesterase inhibitor, and a stimulator of calcium-release channels. Despite the individual genetic variabilities, distinct mechanisms have been demonstrated to improve physical performance, thermogenesis, lipolysis, insulin sensitivity, and hormonal modulation. Thus, coffee consumption and caffeine supplementation may enhance physical and mental performance and may improve metabolic variables, reducing oxidative stress, inflammation, and insulin resistance. Current data reveal vital aspects of coffee and caffeine consumption in specific populations, although further studies are needed to define clinical interventions with caffeine in obesity and chronic conditions.

Knowledge, attitude, and perception of energy drinks consumption among university students in Jordan

Energy drinks gained popularity after the launch of Red Bull in 1997. Different brands are now available and young adults mainly consume these drinks. This study assesses the knowledge, attitude, and perception of energy drink consumption among university students in Jordan. A validated online survey was used to collect the required data, extracted from Google Forms into an Excel spreadsheet and statistically analysed using Statistical Package for Social Sciences version 24.0. A nationally representative sample of university students with a mean age of 22⋅2 ± 3⋅9 years (n 749) was obtained. The participating students demonstrated a neutral level of knowledge about energy drinks, as the mean score of knowledge = 7⋅1 ± 2⋅2 (out of 12), with 66 % (n 498) of them having consumed energy drinks and experienced their effects. Generally, the study's participants demonstrated a neutral attitude towards energy drinks and 70⋅5 % (n 528) acknowledged that energy drinks increase activity, but more than 70 % of them believed that energy drinks have harmful side effects. It was found that there is a significant (P-value <0⋅5) positive correlation between knowledge score and female gender, studying a medical major, and monthly income. The main reasons for consuming energy drinks were reported to be: to stay awake for longer, help study, and become more energetic. There is a need for more structured awareness campaigns to warn students about the possible side effects of these products in order to reduce the consumption and popularity of these drinks among students.

An Acute Bout of Endurance Exercise Does Not Prevent the Inhibitory Effect of Caffeine on Glucose Tolerance the following Morning

Caffeine reduces glucose tolerance, whereas exercise training improves glucose homeostasis. The aim of the present study was to investigate the effect of caffeine on glucose tolerance the morning after an acute bout of aerobic exercise. Methods: The study had a 2 × 2 factorial design. Oral glucose tolerance tests (OGTT) were performed after overnight fasting with/without caffeine and with/without exercise the evening before. Eight healthy young active males were included (Age 25.5 ± 1.5 years; 83.9 ± 9.0 kg; VO_2max: 54.3 ± 7.0 mL·kg^-1·min^-1). The exercise session consisted of 30 min cycling at 71% of VO_2max followed by four 5 min intervals at 84% with 3 min of cycling at 40% of VO_2max between intervals. The exercise was performed at 17:00 h. Energy expenditure at each session was ~976 kcal. Lactate increased to ~8 mM during the exercise sessions. Participants arrived at the laboratory the following morning at 7.00 AM after an overnight fast. Resting blood samples were taken before blood pressure and heart rate variability (HRV) were measured. Caffeine (3 mg/kg bodyweight) or placebo (similar taste/flavor) was ingested, and blood samples, blood pressure and HRV were measured after 30 min. Next, the OGTTs were initiated (75 g glucose dissolved in 3 dL water) and blood was sampled. Blood pressure and HRV were measured during the OGTT. Caffeine increased the area under curve (AUC) for glucose independently of whether exercise was done the evening before (p = 0.03; Two-way ANOVA; Interaction: p = 0.835). Caffeine did not significantly increase AUC for C-peptides compared to placebo (p = 0.096), and C-peptide response was not influenced by exercise. The acute bout of exercise did not significantly improve glucose tolerance the following morning. Diastolic blood pressure during the OGTT was slightly higher after intake of caffeine, independent of whether exercise was performed the evening before or not. Neither caffeine nor exercise the evening before significantly influenced HRV. In conclusion, caffeine reduced glucose tolerance independently of whether endurance exercise was performed the evening before. The low dose of caffeine did not influence heart rate variability but increased diastolic blood pressure slightly.

Consumption patterns of energy drinks in university students: A systematic review and meta-analysis

OBJECTIVES

Energy drink (ED) use is promoted to stimulate mental and/or physical activity, and their popularity has increased over the years, especially among young people. However, the use of EDs is often improper, and can induce adverse effects for human health. The purpose of this systematic review and meta-analysis was to analyze the literature to characterize the prevalence of ED consumption and motivations for use among undergraduate students. Furthermore, adverse effects and health-related behaviors associated with ED consumption were explored.

METHODS

This systematic review was carried out according to the Preferred Reporting Items for Systematic Review and Meta-Analysis guidelines, and the PubMed, Scopus, and Web of Science databases were used for data research.

RESULTS

A total of 71 articles published between 2007 and 2021 met the inclusion criteria and were included in the review. The estimated overall prevalence of ED consumption was 42.9% in undergraduate students (95% confidence interval, 42.5%-43.3%), with significant heterogeneity among studies (Q test: P < 0.001; I² = 99.4%). The main reasons for use were engagement in study, projects or examinations, stay awake or alert, and physical activity/sport engagement. Sleep disturbance and increased heart rate or blood pressure were the most commonly reported adverse effects. ED consumption was frequently associated with alcohol use and smoking.

CONCLUSIONS

These findings suggest that the inappropriate use of EDs and related unhealthy behaviors should be identified early, and addressed through effective educational interventions.<END ABSTRACT>.

A compositional analysis study of body composition and cardiometabolic risk factors

OBJECTIVE

This cross-sectional study used compositional data analysis (CoDA) to do the following: 1) analyze the relative associations between fat and lean tissues with cardiometabolic risk factors; and 2) estimate how these risk factors would change if equivalent mass was displaced from one tissue to another. Differences between CoDA and traditional regression were explored.

METHODS

A total of 397 adults with overweight or obesity were studied. Body composition consisted of visceral fat, abdominal subcutaneous fat, peripheral subcutaneous fat, other fat depots, skeletal muscle, and other lean tissues. The outcomes were a continuous metabolic syndrome score (primary outcome) and eight other cardiometabolic risk factors (secondary outcomes). Associations were examined using CoDA and traditional linear regression.

RESULTS

Visceral fat mass, relative to the mass of the remaining tissues, was significantly associated with the metabolic syndrome score and five of eight remaining risk factors (p < 0.05). The relative contribution of the remaining tissues was not consistently associated with the study outcomes. Displacing equivalent mass from visceral fat into the remaining tissues was associated with meaningful decreases in the metabolic syndrome score. Regression estimates for CoDA and traditional regression differed in size and statistical significance.

CONCLUSIONS

These CoDA findings reinforce that excess visceral fat contributes to less-favorable cardiometabolic risk factors.

Effects of Aerobic Exercise Concurrent with Caffeine Supplementation on Weight and Body Fat Among Overweight Women

Background: Obesity and overweight are among serious global epidemics that significantly threaten human health, especially among women. Objectives: This study aimed to assess the concurrent effects of 6-week caffeine supplementation with moderate-intensity aerobic exercise on weight and body fat among overweight women. Methods: Thirty overweight females (age: 36.47 ± 6.48 years; BMI: 27.61 ± 1.54 kg/m2; mean ± SD) with a sedentary lifestyle were recruited to the study. The participants were randomly allocated to the experimental group, EC (exercise + caffeine) group, who took 100 milligrams of caffeine of the “API” brand supplement 30 minutes before exercise training (n = 15) or control group, EP (exercise + placebo) (n = 15). All participants performed moderate-intensity aerobic exercise with an intensity of 40 to 60% of heart rate reserve based on the individual's exercise test for 30 minutes, three days a week for six weeks. Measurements, including the percentage of body fat, waist circumference, and skinfold (suprailiac, abdominal), were done two times, at baseline and after six weeks of exercising. Results: There were no significant differences between control and experimental groups related to weight (P = 0.22), percentage body fat (P = 0.88), and other measurements after six weeks. Conclusions: 6 weeks of caffeine supplementation combined with moderate-intensity aerobic exercise without dietary interventions couldn’t make a significant reduction in weight and central or total body fat among overweight women.

The Effects of Exercise During a 10-Week Basic Military Training Program on the Physical Fitness and the Body Composition of the Greek Naval Cadets

INTRODUCTION

The period of basic military training (BMT) is a sudden change in the individual habits of the trainees and is characterized by significant improvements in body composition such as the percentage of body fat (%BF) and lean body mass (BM). Research has shown that physical activity during the period of BMT lasting 7-10 weeks has positive effects on the physical condition and BM of cadets. The purpose of this study was to examine the effects of training combining cardiovascular conditioning, circuit strength training, swimming, team sports, and obstacle course on physical fitness and body composition during a 10-week BMT period over 4 years in the Hellenic Naval Academy (HNA).

MATERIALS AND METHODS

The sample consisted of 185 Greek cadets of the HNA (age: 18.4 ± 0.7 years, height: 1.77 ± 6.7 m, BM: 72.6 ± 9.1 kg), of which 153 was male (age: 18.3 ± 0.6 years, height: 1.79 ± 5.8 cm, BM: 75.3 ± 7.6 kg) and 32 was female (age: 18.6 ± 0.9 years, height: 1.68 ± 2.8 cm, BM: 59.9 ± 3.1 kg).The cadets participated each year for 4 years in the BMT, performing 94 training sessions, five times a week. The weekly training program included cardiovascular conditioning, circuit strength training, swimming, team sports, and obstacle course. The measurements of the participants before and after BMT were on BM, %BF, and body mass index (BMI); on the number of sit-ups (SU1), push-ups (PU1), and pull-ups (PullU1) in 1 minute; and on the 12-minute aerobic Cooper test (12-min run).

RESULTS

The results of the study showed that the BM of the cadets decreased significantly by 2.5%, (t184 = 17.591, P < .01), in men by 2.7% (t152 = 16.243, P < .01) and in women by 2.2% (t31 = 9.280, P < .01). Body mass index (BMI) decreased significantly by 2.6% (t184 = 17.681, P < .01), in men by 3.0% (t152 = 16.046, P < .01) and in women by 2.3% (t31 = 9.224, P < 0.01). Reduction in %BF in all cadets reached 11.3% (t184 = 8.134, P < .01), for men -14.8% (t152 = 8.918, P < .01) and women -2.1% (t31 = 0.860, P > .05) without significant differences between the measurements.The number of push-ups in 1 minute (PU1) significantly increased by 27.6% (t184 = -27.813, P < .01), in women by +35.6% (t31 = 13,864, P < .01). The number of sit-ups in 1 minute (SU1) significantly increased by 27.3% (t184 = -30.501, P < .01), for men +28.8% (t152 = -29.862, P < .01). The number of pull-ups in 1 minute (PullU1) reached 20.8% (t184 = -13.426, P < .01) in total, at similar levels in men (t152 = -13.918, p < .01) and women (t31 = -2.820, P < .01).On the 12-min run, the significant improvement exceeded 10.8% (t184 = -45.289, P < .01), in men by 11.1% (t152 = -45.222, P < .01) while in women by 9.0% (t31 = 15.709, P < .01).

CONCLUSIONS

The results of this study showed that 10 weeks of BMT, which combined cardiovascular conditioning, circuit strength training, swimming, team sports, and obstacle course improved the body composition, cardiorespiratory endurance, and the strength of the Greek HNA cadets.

Caffeine-Containing Energy Shots Cause Acute Impaired Glucoregulation in Adolescents

Caffeine-containing, nutritionally fortified energy shots are consumed at high rates by adolescents, yet little is known about their metabolic impact. The purpose of this study was to examine the consequences of small format, caffeinated energy shots on glucose metabolism and gastrointestinal hormone secretion in adolescents. Twenty participants aged 13-19 years participated in a double-blind, randomized cross-over study consisting of two trials separated by 1-4 weeks. Participants consumed a volume-matched caffeinated energy shot (CAF, 5 mg/kg) or a decaffeinated energy shot (DECAF) followed by a 2 h oral glucose tolerance test. Blood samples were collected and area under the curve (AUC) calculated for glucose, insulin and gut and metabolic hormones. Consumption of CAF resulted in a 25% increase in glucose and a 26% increase in insulin area under the curve (AUC, p = 0.037; p < 0.0001) compared to DECAF. No impact on gut hormones was observed. To further characterize responses, individuals were classified as either slow or fast caffeine metabolizers based on an allele score. Glucose intolerance was greater in genetically fast vs. slow caffeine metabolizers and differences between groups were supported by distinct serum metabolomics separation. Consumption of caffeine-containing energy shots results in acute impaired glucoregulation in healthy adolescents as characterized by hyperinsulinemia following an oral glucose challenge.

Antiobesity and anti-inflammation effects of Hakka stir-fried tea of different storage years on high-fat diet-induced obese mice model via activating the AMPK/ACC/CPT1 pathway

Background

As a typical representative of metabolic syndrome, obesity is also one of the extremely dangerous factors of cardiovascular diseases. Thus, the prevention and treatment of obesity has gradually become a global campaign. There have been many reports that green tea is effective in preventing obesity, but as a kind of green tea with regional characteristics, there have been no reports that Hakka stir-fried tea (HT) of different storage years has a weight loss effect.

Aims

The aim was to investigate the effect of HT in diet-induced obese mice.

Methods

The mice were divided into five groups as follows: the control group received normal diet; the obese model group received high-fat diet; and HT2003, HT2008, and HT2015 groups, after the induction of obesity via a high-fat diet, received HT of different storage years treatment for 6 weeks, respectively.

Results

It was observed that HT decreased the levels of serum and liver triglyceride; the ratio of liver to body weight; accumulation of epididymal, perirenal, and mesenteric fat; the degree of hepatic steatosis; and adipocyte hypertrophy, with the concomitant reduction of body weight. Moreover, HT decreased the expression levels of proinflammatory cytokines tumor necrosis factor α (TNF α), inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) and reduced fatty acid synthase (FAS) activity in liver tissue of obese mice. In addition, HT treatment also increased the phosphorylation of AMP-activated protein kinase (AMPK) and its direct downstream proteins, acetyl coenzyme A carboxylase (ACC), and carnitine palmitoyltransferase I (CPT-1), which participate in FAS pathway.

Conclusions

These findings demonstrate that HT treatment has a potential protection on high-fat diet-induced obesity mice via activating the AMPK/ACC/CPT1 pathway, and to a certain extent, it has nothing to do with the storage time of three kinds of HT.

Beneficial Impact of Semicarbazide-Sensitive Amine Oxidase Inhibition on the Potential Cytotoxicity of Creatine Supplementation in Type 2 Diabetes Mellitus

Creatine supplementation of the population with type 2 diabetes mellitus (T2DM) combined with an exercise program is known to be a possible therapy adjuvant with hypoglycemic effects. However, excessive administration of creatine leads to the production of methylamine which is deaminated by the enzyme semicarbazide-sensitive amine oxidase (SSAO) and as a result, cytotoxic compounds are produced. SSAO activity and reaction products are increased in the serum of T2DM patients. Creatine supplementation by diabetics will further augment the activity of SSAO. The current review aims to find a feasible way to ameliorate T2DM for patients who exercise and desire to consume creatine. Several natural agents present in food which are involved in the regulation of SSAO activity directly or indirectly are reviewed. Particularly, zinc-α2-glycoprotein (ZAG), zinc (Zn), copper (Cu), histamine/histidine, caffeine, iron (Fe), and vitamin D are discussed. Inhibiting SSAO activity by natural agents might reduce the potential adverse effects of creatine metabolism in population of T2DM.

An experimental study on perceptions of energy drink ads among youth and young adults in Canada

Current regulations in Canada prohibit the marketing of caffeinated energy drinks (CEDs) for use during sports, with alcohol, and by children. The study examined perceptions of CED ads in association with sports and alcohol use, as well as target age groups. An online survey was conducted in 2015 with youth and young adults aged 12-24 years (n = 2010). Participants completed three experiments in which they were randomized to view CED advertisements: 1) sports/party-themed ads, 2) sports-themed ad, and 3) party-themed ad, vs. control 'product information' ads. For each ad, participants were asked about perceived target age group, and if the ad promoted using CEDs during sports and with alcohol. Logistic regression models were fitted to test differences in outcomes between conditions. The majority of respondents reported that the ads, across all themes, targeted people their age. In experiment 1, both sports/party-themed ads were more likely to be perceived as promoting use of CEDs during sports (AOR = 13.32; 95% CI 9.90, 17.91, and AOR = 9.73; 95% CI 7.38, 12.81, respectively), and with alcohol (AOR = 8.55; 95% CI 6.37, 11.48, and AOR = 2.81; 95% CI 2.08, 3.78, respectively), compared to the control ad. In experiment 2, the sports-themed ad was more likely to be perceived as promoting use of CEDs during sports (AOR = 15.02; 95% CI 11.83, 19.08), but not with alcohol, compared to the control ad. In experiment 3, the party-themed ad was more likely to be perceived as promoting use of CEDs with alcohol (AOR = 13.79; 95% CI 10.69, 17.78), but not during sports, compared to the control ad. Ads from leading energy drink brands are perceived as targeting young people and encouraging energy drink use during sports and with alcohol, despite Canadian regulations prohibiting these marketing practices.

Thrombotic Thrombocytopenic Purpura Cases and Consumption of Large Quantities of Energy Drink: Related or Coincidence?

The vast majority of cases of thrombotic thrombocytopenic purpura (TTP) are the result of acquired antibodies which inhibit the activity of the ADAMTS13 enzyme. Acquired TTP is more frequently seen in young females or in individuals with autoimmune disease. The development of antibodies against ADAMTS13 may also result from the administration or consumption of drugs and other substances. However, specific laboratory tests to identify the pathogenic mechanism of a particular drug may not be available, and the role of a potentially implicated drug or other ingested substance may not be clear. In this report we present 2 acquired TTP cases involving the consumption of a large amount of energy drink.

Exposure and perceptions of marketing for caffeinated energy drinks among young Canadians

OBJECTIVE

To examine exposure to energy drink marketing among youth and young adults, and test perceptions of energy drink advertisements (ads) regarding target audience age and promoting energy drink use during sports.

DESIGN

A between-group experiment randomly assigned respondents to view one of four energy drink ads (sport-themed or control) and assessed perceptions of the ad. Regression models examined marketing exposure and perceptions.

SETTING

Online survey (2014).

SUBJECTS

Canadians aged 12-24 years (n 2040) from a commercial panel.

RESULTS

Overall, 83 % reported ever seeing energy drink ads through at least one channel, including on television (60 %), posters/signs in stores (49 %) and online (44 %). Across experimental conditions, most respondents (70·1 %) thought the ad they viewed targeted people their age or younger, including 42·2 % of those aged 12-14 years. Two sport-themed ads were more likely to be perceived as targeting a younger audience (adjusted OR (95 % CI): 'X Games' 36·5 %, 4·16 (3·00, 5·77); 'snowboard' 19·2 %, 1·50 (1·06, 2·13)) v. control (13·3 %). Participants were more likely to believe an ad promoted energy drink use during sports if they viewed any sport-themed ad ('X Games' 69·9 %, 8·29 (6·24, 11·02); 'snowboard' 76·7 %, 11·85 (8·82, 15·92); 'gym' 66·8 %, 7·29 (5·52, 9·64)) v. control (22·0 %). Greater reported exposure to energy drink marketing was associated with perceiving study ads as promoting energy drink use during sports.

CONCLUSIONS

Energy drink marketing has a high reach among young people. Ads for energy drinks were perceived as targeting youth and promoting use during sports. Such ads may be perceived as making physical performance claims, counter to Canadian regulations.

Symptoms Attributed to Consumption of Caffeinated Beverages in Adolescents

Purpose: Pediatric caffeine use has become increasingly prevalent. The American Academy of Pediatrics discourages caffeine use by children and adolescents due to its adverse impact on sleep and blood pressure. The objective of this study was to measure prevalence of physical and emotional symptoms related to caffeine consumption among adolescents receiving primary care. Methods: A convenience sample of patients (N = 179; 73% female) aged 12-17 presenting for routine primary care completed the Composite International Diagnostic Interview Substance Abuse Module questionnaire, which included questions regarding use of caffeine. Descriptive statistics were used to summarize prevalence of caffeine use and caffeine-related symptoms. Associations of number of caffeine-related symptoms with age, gender, and race/ethnicity were also analyzed. Results: Sixty-seven percent of participants (n = 120) reported past 30-day caffeinated beverage consumption. Of those, 68% (n = 82) reported at least one symptom or problem attributed to caffeine use or withdrawal, including caffeine cravings, 24% (n = 29); frequent urination, 21% (n = 25); difficulty falling asleep, 18% (n = 22); and feeling anxious, 3.3% (n = 4). Conclusions: In our sample, caffeinated beverage consumption by adolescents was frequently associated with physical and emotional symptoms, as well as problems attributed to use.

Performance effects and metabolic consequences of caffeine and caffeinated energy drink consumption on glucose disposal

This review documents two opposing effects of caffeine and caffeine-containing energy drinks, i.e., their positive effects on athletic performance and their negative impacts on glucose tolerance in the sedentary state. Analysis of studies examining caffeine administration prior to performance-based exercise showed caffeine improved completion time by 3.6%. Similar analyses following consumption of caffeine-containing energy drinks yielded positive, but more varied, benefits, which were likely due to the diverse nature of the studies performed, the highly variable composition of the beverages consumed, and the range of caffeine doses administered. Conversely, analyses of studies administering caffeine prior to either an oral glucose tolerance test or insulin clamp showed a decline in whole-body glucose disposal of ~30%. The consequences of this resistance are unknown, but there may be implications for the development of a number of chronic diseases. Both caffeine-induced performance enhancement and insulin resistance converge with the primary actions of caffeine on skeletal muscle.

Energy drink consumption in europe: a review of the risks, adverse health effects, and policy options to respond

With the worldwide consumption of energy drinks increasing in recent years, concerns have been raised both in the scientific community and among the general public about the health effects of these products. Recent studies provide data on consumption patterns in Europe; however, more research is needed to determine the potential for adverse health effects related to the increasing consumption of energy drinks, particularly among young people. A review of the literature was conducted to identify published articles that examined the health risks, consequences, and policies related to energy drink consumption. The health risks associated with energy drink consumption are primarily related to their caffeine content, but more research is needed that evaluates the long-term effects of consuming common energy drink ingredients. The evidence indicating adverse health effects due to the consumption of energy drinks with alcohol is growing. The risks of heavy consumption of energy drinks among young people have largely gone unaddressed and are poised to become a significant public health problem in the future.

Endometrial cancer in relation to coffee, tea, and caffeine consumption: a prospective cohort study among middle-aged women in Sweden

This study aimed to add to prospective data on the possible inverse association between coffee consumption and endometrial cancer risk, already supported by several case-control studies. Coffee and tea consumption and possible confounding factors were assessed among 42,270 women aged 30-49 years at enrollment in 1991-1992 in the Swedish Women's Lifestyle and Health cohort study, with complete follow-up through 2009. We calculated caffeine intake per day; Cox proportional hazard models were used to estimate multivariable relative risks (mRR) for endometrial cancer with 95% confidence intervals (CIs). One hundred forty-four endometrial cancers were diagnosed during follow-up. Women with and without endometrial cancer had a similar mean daily coffee consumption (549 vs. 547 g), tea consumption (104 vs. 115 g), and caffeine intake (405 vs. 406 mg). Compared to those consuming <2 cups of coffee per day, women consuming >3 cups had a mRR of 1.56 (95% CI: 0.94-2.59; P for trend = 0.17). Compared with the lowest tertile of caffeine intake, the highest tertile had a mRR of 1.32 (95% CI: 0.87-1.99; P for trend = 0.27). Our study provides no convincing evidence of an association between coffee consumption, tea consumption, or caffeine intake and endometrial cancer risk among middle-aged women.

Sulfonylurea induction of caffeine-enhanced insulin secretion and reduction of glycemic levels in diabetic rats

CONTEXT

Caffeine can stimulate insulin secretion by attenuating hyperglycemia in diabetes models with significant reduction of pancreatic functional β cells. Knowledge of these mechanisms could contribute to new strategies for treating diabetes.

OBJECTIVE

This study evaluated the effects of caffeine and physical exercise on glycemic and insulin responses in diabetic rats.

MATERIALS AND METHODS

The diabetes model was induced by intraperitoneal administration of 60 mg/kg of streptozotocin (STZ). Animals were divided into six groups: control, caffeine, STZ control, STZ caffeine, STZ sulfonylurea, and STZ caffeine + sulfonylurea. Acutely, control animals received 6 mg of caffeine and 10 mg/kg sulfonylurea or 10 mg/kg saline. Animals were sacrificed after physical exercise; blood samples were collected for glucose, glycerol, lactate, and insulin analyses. Cardiovascular responses were recorded before and after treatments. A one-way ANOVA and the post hoc Student-Newman-Keuls test were used to analyze statistical differences between treatments (p < 0.05).

RESULTS

About 6 mg/kg of caffeine did not alter cardiovascular responses, but promoted blood glucose reduction after 60 min of exercise when compared to animals in the control groups (387-187 mg/dL; p < 0.05). Insulin levels increased significantly (0.6-10 µU/mL; p < 0.05) in rats that received acute caffeine treatment associated with sulfonylurea compared to rats in the other groups.

DISCUSSION AND CONCLUSION

Acute caffeine intake with exercise can increase glucose uptake enhancing insulin secretion stimulated by sulfonylurea in β cells-deficient pancreas. The results indicate the potential use of caffeine as a strategy for glycemic and insulin control in diabetes.

Measurement of muscle insulin sensitivity in obese men

AIMS

In 2007, a novel estimate of skeletal muscle insulin sensitivity was derived from the oral glucose tolerance test (OGTT). The aim of this investigation is to assess whether and to what extent the proposed index of skeletal muscle insulin sensitivity derived from the OGTT was associated with muscle insulin sensitivity measured using the hyperinsulinemic-euglycaemic clamp technique.

METHODS

Forty-six middle-aged, abdominally obese men (age 44 ± 8 years, waist circumference 107.4 ± 6.2) were studied. Each participant participated in a 2-hour, 75-g OGTT and a 3-hour hyperinsulinemic-euglycaemic clamp protocol.

RESULTS

The OGTT-derived index of muscle insulin sensitivity correlated with muscle insulin sensitivity measured with the insulin clamp (r=0.55, P<0.01), however, the standard error of estimate (SEE) when predicting muscle insulin sensitivity by the OGTT-derived index was 5.3 (50%).

CONCLUSION

Our findings suggest that despite a statistically significant association between the two methods, the OGTT approach lacks precision and is not a useful method for estimating skeletal muscle insulin sensitivity in abdominally obese men.

Caffeine and glucose homeostasis during rest and exercise in diabetes mellitus

Caffeine is a substance that has been used in our society for generations, primarily for its effects on the central nervous system that causes wakefulness. Caffeine supplementation has become increasingly more popular as an ergogenic aid for athletes and considerable scientific evidence supports its effectiveness. Because of their potential to alter energy metabolism, the effects of coffee and caffeine on glucose metabolism in diabetes have also been studied both epidemiologically and experimentally. Predominantly targeting the adenosine receptors, caffeine causes alterations in glucose homeostasis by decreasing glucose uptake into skeletal muscle, thereby causing elevations in blood glucose concentration. Caffeine intake has also been proposed to increase symptomatic warning signs of hypoglycemia in patients with type 1 diabetes and elevate blood glucose levels in patients with type 2 diabetes. Other effects include potential increases in glucose counterregulatory hormones such as epinephrine, which can also decrease peripheral glucose disposal. Despite these established physiological effects, increased coffee intake has been associated with reduced risk of developing type 2 diabetes in large-scale epidemiological studies. This review paper highlights the known effects of caffeine on glucose homeostasis and diabetes metabolism during rest and exercise.

Total body water and its compartments are not affected by ingesting a moderate dose of caffeine in healthy young adult males

Acute and chronic caffeine intakes have no impact on hydration status (R.J. Maughan and J. Griffin, J. Hum. Nutr. Diet. 16(6): 411-420, 2003), although no research has been conducted to analyze the effects using dilution techniques on total-body water (TBW) and its compartments. Therefore, the aim of this study was to investigate the effects of a moderate dose of caffeine on TBW, extracellular water (ECW), and intracellular water (ICW) during a 4-day period in active males. Thirty men, nonsmokers and low caffeine users (<100 mg·day(-1)), aged 20-39 years, participated in this double-blind, randomized, crossover trial (ClinicalTrials.gov: No. NCT01477294). The study included 2 conditions (5 mg·kg(-1)·day(-1) of caffeine and placebo (malt-dextrin)) of 4 days each, with a 3-day washout period. TBW and ECW were assessed by deuterium oxide and sodium bromide dilution, respectively, whereas ICW was calculated as TBW minus ECW. Body composition was assessed by dual-energy X-ray absorptiometry. Physical activity (PA) was assessed by accelerometry and water intake was assessed by dietary records. Repeated-measures analysis of variance (ANOVA) was used to test main effects. No changes in TBW, ECW, or ICW and no interaction between the randomly assigned order of treatment and time were observed (p > 0.05). TBW, ECW, and ICW were unrelated to fat-free mass, water ingestion, and PA (p > 0.05). These findings indicate that a moderate caffeine dose, equivalent to approximately 5 espresso cups of coffee or 7 servings of tea, does not alter TBW and fluid distribution in healthy men, regardless of body composition, PA, or daily water ingestion.

Caffeine ingestion impairs insulin sensitivity in a dose-dependent manner in both men and women

The effects of alkaloid caffeine on insulin sensitivity have been investigated primarily in men, and with a single caffeine dose most commonly of 5-6 mg·kg(-1) of body weight (BW). It is unknown if the effects of caffeine on glucose homeostasis are sex-specific and (or) dose-dependent. This study examined whether caffeine ingestion would disrupt glucose homeostasis in a dose-dependent or threshold manner. It also examined whether sex-specific responses to caffeine exist. It was hypothesized that women would have an exaggerated response to caffeine, and that caffeine would only impair glucose metabolism once a threshold was reached. Twenty-four healthy volunteers (12 males, 12 females) participated in 4 trials, in a crossover, randomized, and double-blind fashion. They ingested caffeine (1, 3, or 5 mg·kg(-1) of BW) or placebo followed, 1 h later, by a 2-h oral glucose tolerance test. Glucose, insulin, C-peptide area under the curve (AUC), and insulin sensitivity index data were fitted to a segmented linear model to determine dose-responses. There were no differences between sexes for any endpoints. Regression slopes were significantly different from zero (p < 0.05) for glucose, insulin, and C-peptide AUCs, with thresholds being no different from zero. Increasing caffeine consumption by 1 mg·kg(-1) of BW increased insulin and C-peptide AUCs by 5.8% and 8.7%, respectively. Despite this exaggerated insulin response, glucose AUC increased by 11.2 mmol per 120 min·L(-1) for each mg·kg(-1) BW consumed. These results showed that caffeine ingestion disrupted insulin sensitivity in a dose-dependent fashion beginning at very low doses (0-1 mg·kg(-1) BW) in both healthy men and women.

Insulin resistance and cancer: epidemiological evidence

Epidemiological research into insulin resistance has focused on excess body weight, type 2 diabetes mellitus (DM), physical activity, and coffee consumption. These common modifiable factors have also been suggested to play a role in the process of carcinogenesis via associations with insulin resistance. Findings of systematic literature reviews and meta-analyses have generally supported an association between excess body weight and DM with an increased risk of colon cancer in males, and of liver, pancreatic, and endometrial cancers. Inverse relationships between these cancers and physical activity and coffee consumption have been shown, both of which are known to reduce the risk of DM. Interventions directed at or involving these variables should contribute to decreasing the risk of insulin resistance-associated cancer.

Aerobic performance and body composition changes during military service

OBJECTIVE

To examine the association between aerobic performance and body composition changes by body mass index (BMI).

DESIGN

6-12 months' follow-up during military service.

SETTING

Conscripts entering military service in 2005 in Sodankylä Jaeger Brigade (Finland).

SUBJECTS

945 men (19 years, SD 1 years).

MAIN OUTCOME MEASURES

Height, weight, waist circumference, BMI, and aerobic performance (Cooper test) were recorded. Body composition was measured by bioelectrical impedance analysis (BIA). The measured parameters were fat mass (FM), fat free mass (FFM), and visceral fat area (VFA). All the measurements were performed at the beginning and end of service.

RESULTS

On average, the military training period improved the running distance by 6.8% (169 m, p < 0.001) and the improvements were more pronounced in overweight (223.9 m/9.5%, p < 0.001) and obese (273.3 m/13.6%, p < 0.001) conscripts. A strong inverse correlation between aerobic performance and body composition changes was observed, especially for weight (r = -0.305, p < 0.001) and VFA (r = -0.465, p < 0.001). A significant association between aerobic performance and changes in weight (p < 0.001), waist circumference (p < 0.001), FM (p < 0.001), and VFA (p < 0.001) by BMI was detected. The associated decrease in weight, waist circumference, FM, and VFA with improved aerobic performance was more substantial between overweight and obese compared with normal-weight subjects.

CONCLUSIONS

Favourable changes in body composition are associated with improved aerobic performance during a physical training period such as military service. These findings are pronounced among overweight and obese men and can be applied at the population level in reducing obesity and co-morbidities.

Role of coffee in modulation of diabetes risk

Coffee consumption has been associated with a lower risk of type 2 diabetes. This association does not depend on race, gender, geographic distribution of the study populations, or the type of coffee consumed (i.e., caffeinated or decaffeinated). This review discusses the strength of this relationship, examines the possibility that the pattern of coffee consumption could influence the association, and evaluates the possible relationship between coffee consumption and other risk factors associated with diabetes. Particular attention is paid to the identification, on the basis of the scientific evidence, of the possible mechanisms by which coffee components might affect diabetes development, especially in light of the paradoxical effect of caffeine on glucose metabolism. In addition to the role of coffee in reducing the risk of developing type 2 diabetes, the possible role of coffee in the course of the illness is explored. Finally, the possibility that coffee can also affect the risk of other forms of diabetes (e.g., type 1 diabetes and gestational diabetes) is examined.

A survey of energy drinks consumption practices among student -athletes in Ghana: lessons for developing health education intervention programmes

BACKGROUND

Globally, young adults and college athletes are primary targets of the marketing campaigns of energy drink companies. Consequently, it is reported that young adults and college athletes consume energy drinks frequently. The purpose of this study was to determine the prevalence of energy drink consumption among student-athletes selected from seven public universities in Ghana. The study assessed the energy drink consumption patterns, types usually consumed, frequency of consumption and reasons why athletes consumed energy drinks.

METHODS

A total number of 180 student-athletes gave their consent to participate in the study and completed a questionnaire which was administered during an inter-university sports competition.

RESULTS

Most of the participants (62.2%) reported consuming at least one can of energy drink in a week. A high proportion (53.6%) of the respondents who drink energy drinks indicated that they did so to replenish lost energy after training or a competition. Other reasons given as to why energy drinks were consumed by the study participants included to provide energy and fluids to the body (25.9%), to improve performance (9.8%) and to reduce fatigue (5.4%).

CONCLUSION

These results suggest the need to plan health education programmes to particularly correct some wrong perceptions that athletes have regarding the benefits of energy drinks and also create awareness among student-athletes about the side effects of excessive intake of energy drinks.

Chlorogenic acid stimulates glucose transport in skeletal muscle via AMPK activation: a contributor to the beneficial effects of coffee on diabetes

Chlorogenic acid (CGA) has been shown to delay intestinal glucose absorption and inhibit gluconeogenesis. Our aim was to investigate the role of CGA in the regulation of glucose transport in skeletal muscle isolated from db/db mice and L6 skeletal muscle cells. Oral glucose tolerance test was performed on db/db mice treated with CGA and soleus muscle was isolated for 2-deoxyglucose transport study. 2DG transport was also examined in L6 myotubes with or without inhibitors such as wortmannin or compound c. AMPK was knocked down with AMPKα1/2 siRNA to study its effect on CGA-stimulated glucose transport. GLUT 4 translocation, phosphorylation of AMPK and Akt, AMPK activity, and association of IRS-1 and PI3K were investigated in the presence of CGA. In db/db mice, a significant decrease in fasting blood sugar was observed 10 minutes after the intraperitoneal administration of 250 mg/kg CGA and the effect persisted for another 30 minutes after the glucose challenge. Besides, CGA stimulated and enhanced both basal and insulin-mediated 2DG transports in soleus muscle. In L6 myotubes, CGA caused a dose- and time-dependent increase in glucose transport. Compound c and AMPKα1/2 siRNA abrogated the CGA-stimulated glucose transport. Consistent with these results, CGA was found to phosphorylate AMPK and ACC, consistent with the result of increased AMPK activities. CGA did not appear to enhance association of IRS-1 with p85. However, we observed activation of Akt by CGA. These parallel activations in turn increased translocation of GLUT 4 to plasma membrane. At 2 mmol/l, CGA did not cause any significant changes in viability or proliferation of L6 myotubes. Our data demonstrated for the first time that CGA stimulates glucose transport in skeletal muscle via the activation of AMPK. It appears that CGA may contribute to the beneficial effects of coffee on Type 2 diabetes mellitus.

Waist circumference adjusted for body mass index and intra-abdominal fat mass

Background

The association between waist circumference (WC) and mortality is particularly strong and direct when adjusted for body mass index (BMI). One conceivable explanation for this association is that WC adjusted for BMI is a better predictor of the presumably most harmful intra-abdominal fat mass (IAFM) than WC alone. We studied the prediction of abdominal subcutaneous fat mass (ASFM) and IAFM by WC alone and by addition of BMI as an explanatory factor.

Methodology/Principal Findings

WC, BMI and magnetic resonance imaging data from 742 men and women who participated in clinical studies in Canada and Finland were pooled. Total adjusted squared multiple correlation coefficients (R²) of ASFM and IAFM were calculated from multiple linear regression models with WC and BMI as explanatory variables. Mean BMI and WC of the participants in the pooled sample were 30 kg/m² and 102 cm, respectively. WC explained 29% of the variance in ASFM and 51% of the variance in IAFM. Addition of BMI to WC added 28% to the variance explained in ASFM, but only 1% to the variance explained in IAFM. Results in subgroups stratified by study center, sex, age, obesity level and type 2 diabetes status were not systematically different.

Conclusion/Significance

The prediction of IAFM by WC is not improved by addition of BMI.

Caffeine modulates phosphorylation of insulin receptor substrate-1 and impairs insulin signal transduction in rat skeletal muscle

Caffeine decreases insulin sensitivity and insulin-stimulated glucose transport in skeletal muscle; however, the precise mechanism responsible for this deleterious effect is not understood fully. We investigated the effects of incubation with caffeine on insulin signaling in rat epitrochlearis muscle. Caffeine (≥1 mM, ≥15 min) suppressed insulin-stimulated insulin receptor substrate (IRS)-1 Tyr(612) phosphorylation in a dose- and time-dependent manner. These responses were associated with inhibition of the insulin-stimulated phosphorylation of phosphatidylinositol 3-kinase (PI3K) Tyr(458), Akt Ser(473), and glycogen synthase kinase-3β Ser(9) and with inhibition of insulin-stimulated 3-O-methyl-d-glucose (3MG) transport but not with inhibition of the phosphorylation of insulin receptor-β Tyr(1158/62/63). Furthermore, caffeine enhanced phosphorylation of IRS-1 Ser(307) and an IRS-1 Ser(307) kinase, inhibitor-κB kinase (IKK)-α/β Ser(176/180). Blockade of IKK/IRS-1 Ser(307) by caffeic acid ameliorated the caffeine-induced downregulation of IRS-1 Tyr(612) phosphorylation and 3MG transport. Caffeine also increased the phosphorylation of IRS-1 Ser(789) and an IRS-1 Ser(789) kinase, 5'-AMP-activated protein kinase (AMPK). However, inhibition of IRS-1 Ser(789) and AMPK phosphorylation by dantrolene did not rescue the caffeine-induced downregulation of IRS-1 Tyr(612) phosphorylation or 3MG transport. In addition, caffeine suppressed the phosphorylation of insulin-stimulated IRS-1 Ser(636/639) and upstream kinases, including the mammalian target of rapamycin and p70S6 kinase. Intravenous injection of caffeine at a physiological dose (5 mg/kg) in rats inhibited the phosphorylation of insulin-stimulated IRS-1 Tyr(612) and Akt Ser(473) in epitrochlearis muscle. Our results indicate that caffeine inhibits insulin signaling partly through the IKK/IRS-1 Ser(307) pathway, via a Ca(2+)- and AMPK-independent mechanism in skeletal muscle.

An oral lipid challenge and acute intake of caffeinated coffee additively decrease glucose tolerance in healthy men

Lipid-induced insulin resistance has been investigated primarily with i.v. infusions, and caffeine-induced insulin resistance, with alkaloid caffeine. The effects of orally consumed lipids and coffee have not been established and to our knowledge have never been simultaneously investigated. The goals of this study were to determine whether an oral lipid challenge and caffeinated coffee would disrupt glucose homeostasis and to characterize their respective incretin responses. It was hypothesized that oral ingestion of saturated lipids would impair glucose tolerance and that caffeinated coffee would further hinder glucose management. Ten young, healthy males participated in 5 trials in a randomized, cross-over design. At time 0 h, they underwent an oral fat tolerance test (OFTT: 1 g lipid/kg body weight) or consumed water, followed 5 h later by caffeinated (5 mg/kg) coffee, decaffeinated coffee, or water. At 6 h, volunteers underwent an oral glucose tolerance test (OGTT). Consumption of the OFTT increased glucose concentrations (P < 0.05) after a subsequent OGTT. At 7 h, caffeinated coffee produced the highest glucose concentrations (P < 0.05). Glucagon-like peptide-1 active (GLP-1a) and glucose-dependent insulinotropic polypeptide (GIP) were both increased for up to 6 h in all OFTT trials (P < 0.05). Compared to all other treatments, caffeinated and decaffeinated coffee produced higher GLP-1a response at 6.25 h (P < 0.05), whereas only caffeinated coffee increased GIP secretion (P < 0.05). These results show that oral consumption of lipids and caffeinated coffee can independently and additively decrease glucose tolerance. Incretin hormones could explain at least in part this impaired glucose homeostasis.

Methylxanthines and human health: epidemiological and experimental evidence

When considering methylxanthines and human health, it must be recognized that in many countries most caffeine is consumed as coffee. This is further confounded by the fact that coffee contains many bioactive substances in addition to caffeine; it is rich in phenols (quinides, chlorogenic acid, and lactones) and also has diterpenes (fatty acid esters), potassium, niacin, magnesium, and the vitamin B(3) precursor trigonelline. There is a paradox as consumption of either caffeine or caffeinated coffee results in a marked insulin resistance and yet habitual coffee consumption has repeatedly been reported to markedly reduce the risk for type 2 diabetes. There is strong evidence that caffeine reduces insulin sensitivity in skeletal muscle and this may be due to a combination of direct antagonism of A(1) receptors and indirectly β-adrenergic stimulation as a result of increased sympathetic activity. Caffeine may also induce reduced hepatic glucose output. With the exception of bone mineral, there is little evidence that caffeine impacts negatively on other health issues. Coffee does not increase the risk of cardiovascular diseases or cancers and there is some evidence suggesting a positive relationship for the former and for some cancers, particularly hepatic cancer.

Caffeine and theophylline block insulin-stimulated glucose uptake and PKB phosphorylation in rat skeletal muscles

AIM

Caffeine and theophylline inhibit phosphatidylinositol 3-kinase (PI3-kinase) activity and insulin-stimulated protein kinase B (PKB) phosphorylation. Insulin-stimulated glucose uptake involves PI3-kinase/PKB, and the aim of the present study was to test the hypothesis that caffeine and theophylline inhibit insulin-stimulated glucose uptake in skeletal muscles.

METHODS

Rat epitrochlearis muscles and soleus strips were incubated with insulin and different concentrations of caffeine and theophylline for measurement of glucose uptake, force development and PKB phosphorylation. The effect of caffeine was also investigated in muscles stimulated electrically.

RESULTS

Caffeine and theophylline completely blocked insulin-stimulated glucose uptake in both soleus and epitrochlearis muscles at 10 mm. Furthermore, insulin-stimulated PKB Ser(473) and Thr(308) and GSK-3beta Ser(9) phosphorylation were blocked by caffeine and theophylline. Caffeine reduced and theophylline blocked insulin-stimulated glycogen synthase activation. Caffeine stimulates Ca(2+) release and force development increased rapidly to 10-20% of maximal tetanic contraction. Dantrolene (25 microm), a well-known inhibitor of Ca(2+)-release, prevented caffeine-induced force development, but caffeine inhibited insulin-stimulated glucose uptake in the presence of dantrolene. Contraction, like insulin, stimulates glucose uptake via translocation of glucose transporter-4 (GLUT4). Caffeine and theophylline reduced contraction-stimulated glucose uptake by about 50%, whereas contraction-stimulated glycogen breakdown was normal.

CONCLUSION

Caffeine and theophylline block insulin-stimulated glucose uptake independently of Ca(2+) release, and the likely mechanism is via blockade of insulin-stimulated PI3-kinase/PKB activation. Caffeine and theophylline also reduced contraction-stimulated glucose uptake, which occurs independently of PI3-kinase/PKB, and we hypothesize that caffeine and theophylline also inhibit glucose uptake in skeletal muscles via an additional and hitherto unknown molecule involved in GLUT4 translocation.

Insulin resistance and cancer: epidemiological evidence

Over the last 60 years, Japanese people have experienced a rapid and drastic change in lifestyle, including diet. Suspicions have been raised that so-called 'Westernization', characterized by a high-calorie diet and physical inactivity, is associated with increasing trends in the incidence of cancer of the colon, liver, pancreas, prostate, and breast, as well as type 2 diabetes. Epidemiological evidence from our prospective study, the Japan Public Health Center-based Prospective (JPHC) study, and systematic literature reviews generally support the idea that factors related to diabetes or insulin resistance are associated with an increased risk of colon (mostly in men), liver, and pancreatic cancers. These cancers are inversely associated with physical activity and coffee consumption, which are known to decrease the risk of type 2 diabetes. The suggested mechanism of these effects is that insulin resistance and the resulting chronic hyperinsulinemia and increase in bioavailable insulin-like growth factor 1 (IGF1) stimulate tumor growth. In contrast, associations with diabetes are less clear for cancer of the colon in women, and breast and prostate, which are known to be related to sex hormones. The effect of insulin resistance or body fat on sex-hormone production and bioavailability may modify their carcinogenic effect differently from cancers of the colon in men, and liver and pancreas. In conclusion, there is substantial evidence to show that cancers of the colon, liver, and pancreas are associated with insulin resistance, and that these cancers can be prevented by increasing physical activity, and possibly coffee consumption.

Effects of commercial energy drink consumption on athletic performance and body composition

Energy drinks are frequently marketed to individuals interested in athletics and an active lifestyle. From 2001 to 2008, estimates of energy drink use in adolescent to middle-aged populations ranged from 24% to 56%. Most energy drinks feature caffeine and a combination of other components, including taurine, sucrose, guarana, ginseng, niacin, pyridoxine, and cyanocobalamin. This article examines the evidence for 2 commonly purported uses of energy drinks: athletic performance enhancement and weight loss. Observed ergogenic benefits of energy drinks are likely attributable to caffeine and glucose content. There is conflicting evidence regarding the impact of energy drinks on weight loss, although some data suggest that combining energy drink use with exercise may enhance body fat reduction. As with any pharmacologically active substance, energy drinks are associated with adverse effects. Combining energy drinks with alcohol exacerbates safety concerns and is an increasingly common practice contributing to toxic jock identity among college-aged male athletes. Practitioners should monitor identified populations likely to consume these loosely regulated beverages.

Consumption of caffeinated coffee and a high carbohydrate meal affects postprandial metabolism of a subsequent oral glucose tolerance test in young, healthy males

Caffeine and caffeinated coffee (CC) elicit acute insulin insensitivity when ingested before a carbohydrate load. The effects of CC on glucose tolerance and insulin sensitivity when co-ingested with a high carbohydrate meal and on postprandial metabolism of a subsequent (second) carbohydrate load have not been studied. In a randomised, crossover design, ten healthy males ingested either CC (5 mg caffeine/kg body weight), decaffeinated coffee (DC) or water (W; equal volume) co-ingested with a high glycaemic index cereal followed 3 h later by a 75 g oral glucose tolerance test. After the initial meal, insulin area under the curve (AUC) and insulin sensitivity index did not differ between treatments, although glucose AUC for CC (107 (sem 18) mmol/l × 3 h) and DC (74 (sem 15) mmol/l × 3 h) was greater than W ( − 0·2 (sem 29) mmol/l × 3 h, P < 0·05). After the second carbohydrate load, insulin AUC for CC was 49 % and 57 % greater (P < 0·01) than for DC and W, respectively. Despite the greater insulin response, glucose AUC for CC (217 (sem 24) mmol/l × 2 h) was greater than both DC (126 (sem 11) mmol/l × 2 h, P = 0·01) and W (55 (sem 34) mmol/l × 2 h, P < 0·001). Insulin sensitivity index after the second meal was lower after CC (8·2 (sem 0·9)) compared with both DC (12·4 (sem 1·2), P < 0·01) and W (13·4 (sem 1·4), P < 0·001). Co-ingestion of CC with one meal resulted in insulin insensitivity during the postprandial phase of a second meal in the absence of further CC ingestion. Thus, CC may play a role in daily glycaemic management.

The future of obesity reduction: beyond weight loss

Obesity increases the risk of morbidity and mortality and reduces quality of life independent of age, sex or ethnicity. Leading health authorities recommend weight loss as a primary treatment strategy for obesity reduction--weight loss goals range from 5% to 10% of initial body weight. Intentional weight loss in most adults is associated with a reduction in many of the health complications of obesity. Nonetheless, emerging evidence supports the notion that a lifestyle-modification program characterized by an increase in physical activity and a balanced diet can reduce obesity and the risk of obesity-related comorbid conditions despite minimal or no weight loss. The benefits of such an approach include appreciable reductions in abdominal obesity, visceral fat and cardiometabolic risk factors, and increases in both skeletal muscle mass and cardiorespiratory fitness. Individuals with obesity face a serious challenge if they are to attain even modest weight loss in today's obesogenic environment. Clinicians could encourage positive lifestyle changes in their patients by counseling them that obesity and its associated health risks can be reduced in response to an increase in physical activity with or without weight loss.

Coffee, glucose homeostasis, and insulin resistance: physiological mechanisms and mediators

Epidemiological studies show coffee consumption to be correlated to large risk reductions in the prevalence of type 2 diabetes (T2D). Such correlations are seen with decaffeinated and caffeinated coffee, and occur regardless of gender, method of brewing, or geography. They also exist despite clear evidence showing that caffeine causes acute postprandial hyperglycemia and lower whole-body insulin sensitivity. As the beneficial effects of coffee consumption exist for both decaffeinated and caffeinated coffee, a component of coffee other than caffeine must be responsible. This review examines the specific coffee compounds responsible for coffee's effects on T2D, and their potential physiological mechanisms of action. Being plant-derived, coffee contains many beneficial compounds found in fruits and vegetables, including antioxidants. In fact, coffee is the largest source of dietary antioxidants in industrialized nations. When green coffee is roasted at high temperatures, Maillard reactions create a number of unique compounds. Roasting causes a portion of the antioxidant, chlorogenic acid, to be transformed into quinides, compounds known to alter blood glucose levels. Coffee consumption may also mediate levels of gut peptides (glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1), hormones intimately involved in the regulation of satiety and insulin secretion. Finally, coffee may have prebiotic-like properties, altering gut flora and ultimately digestion. In summary, it is evident that a better understanding of the role of coffee in the development and prevention of T2D has the potential to uncover novel therapeutic targets and nutraceutical formulations for the disease.

Whole-body skeletal muscle mass is not related to glucose tolerance or insulin sensitivity in overweight and obese men and women

The relationship between skeletal muscle mass, visceral adipose tissue, insulin sensitivity, and glucose tolerance was examined in 214 overweight or obese, but otherwise healthy, men (n = 98) and women (n = 116) who participated in various exercise and (or) weight-loss intervention studies. Subjects had a 75 g oral glucose tolerance test and (or) insulin sensitivity measures by a 3 h hyperinsulinemic-euglycemic clamp technique. Whole-body skeletal muscle mass and visceral adipose tissue were measured using a multi-slice magnetic resonance imaging protocol. Total body skeletal muscle mass was not associated with any measure of glucose metabolism in men or women (p > 0.10). These observations remained independent of age and total adiposity. Conversely, visceral adipose tissue was a significant predictor of various measures of glucose metabolism in both men and women with or without control for age and (or) total body fat (p < 0.05). Although skeletal muscle is a primary site for glucose uptake and deposition, these findings suggest that unlike visceral adipose tissue, whole-body skeletal muscle mass per se is not associated with either glucose tolerance or insulin sensitivity in overweight and obese men and women.

Walking: a matter of quantity and quality physical activity for type 2 diabetes management

Walking is often prescribed as a mode of physical activity for people with type 2 diabetes (T2D). We and others have found that although people with T2D may increase the amount that they walk (e.g., more steps per day), improvements in key health outcomes are rarely achieved. We agree that walking is an acceptable approach for people with T2D to meet current clinical practice guidelines, but consideration of both the total number of daily steps and the walking speed of a portion of those total daily steps are necessary to gain health benefit.

Polyphenols in cocoa and cocoa products: is there a link between antioxidant properties and health?

Cocoa and cocoa products have received much attention due to their significant polyphenol contents. Cocoa and cocoa products, namely cocoa liquor, cocoa powder and chocolates (milk and dark chocolates) may present varied polyphenol contents and possess different levels of antioxidant potentials. For the past ten years, at least 28 human studies have been conducted utilizing one of these cocoa products. However, questions arise on which of these products would deliver the best polyphenol contents and antioxidant effects. Moreover, the presence of methylxanthines, peptides, and minerals could synergistically enhance or reduce antioxidant properties of cocoa and cocoa products. To a greater extent, cocoa beans from different countries of origins and the methods of preparation (primary and secondary) could also partially influence the antioxidant polyphenols of cocoa products. Hence, comprehensive studies on the aforementioned factors could provide the understanding of health-promoting activities of cocoa or cocoa products components.

A survey of energy drink consumption patterns among college students

Background

Energy drink consumption has continued to gain in popularity since the 1997 debut of Red Bull, the current leader in the energy drink market. Although energy drinks are targeted to young adult consumers, there has been little research regarding energy drink consumption patterns among college students in the United States. The purpose of this study was to determine energy drink consumption patterns among college students, prevalence and frequency of energy drink use for six situations, namely for insufficient sleep, to increase energy (in general), while studying, driving long periods of time, drinking with alcohol while partying, and to treat a hangover, and prevalence of adverse side effects and energy drink use dose effects among college energy drink users.

Methods

Based on the responses from a 32 member college student focus group and a field test, a 19 item survey was used to assess energy drink consumption patterns of 496 randomly surveyed college students attending a state university in the Central Atlantic region of the United States.

Results

Fifty one percent of participants (n = 253) reported consuming greater than one energy drink each month in an average month for the current semester (defined as energy drink user). The majority of users consumed energy drinks for insufficient sleep (67%), to increase energy (65%), and to drink with alcohol while partying (54%). The majority of users consumed one energy drink to treat most situations although using three or more was a common practice to drink with alcohol while partying (49%). Weekly jolt and crash episodes were experienced by 29% of users, 22% reported ever having headaches, and 19% heart palpitations from consuming energy drinks. There was a significant dose effect only for jolt and crash episodes.

Conclusion

Using energy drinks is a popular practice among college students for a variety of situations. Although for the majority of situations assessed, users consumed one energy drink with a reported frequency of 1 – 4 days per month, many users consumed three or more when combining with alcohol while partying. Further, side effects from consuming energy drinks are fairly common, and a significant dose effect was found with jolt and crash episodes. Future research should identify if college students recognize the amounts of caffeine that are present in the wide variety of caffeine-containing products that they are consuming, the amounts of caffeine that they are consuming in various situations, and the physical side effects associated with caffeine consumption.