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Caffeine intake is related to successful weight loss maintenance
Abstract
The effect of caffeine intake on weight loss maintenance has not been examined in humans. We compared the daily consumption of coffee and caffeinated beverages between 494 weight loss maintainers and 2129 individuals from the general population controlling for sociodemographic variables, body mass index and physical activity level. Weight loss maintainers reported to consume significantly more cups of coffee and caffeinated beverages compared with the participants in the general population sample. Thus, consumption of caffeinated beverages might support weight loss maintenance. Further studies should investigate possible mechanisms.European Journal of Clinical Nutrition advance online publication, 11 November 2015; doi:10.1038/ejcn.2015.183.
... Creatine and Zn combination as a supplement might merit future development after the necessary number of studies. Yes [70] human (healthy) Yes [64] No [61] Caffeine No [107] human Yes [107] human No [68] animal Yes [68] animal No [108] human Yes [108] human Yes [109] human Yes [110] animal ...
... Creatine and Zn combination as a supplement might merit future development after the necessary number of studies. Yes [70] human (healthy) Yes [64] No [61] Caffeine No [107] human Yes [107] human No [68] animal Yes [68] animal No [108] human Yes [108] human Yes [109] human Yes [110] animal ...
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.
... Notably, our study presents a novel finding: a high frequency of coffee consumption and evening coffee consumption are linked to an increased risk of overweight and obesity. Although evidence suggests that coffee consumption can have favorable effects on BMI and weight loss [36,37], recent studies indicate it may also negatively impact body composition [38][39][40]. A recent large-scale genome-wide association study (GWAS) identified genes associated with coffee intake, substance use, and obesity-related traits. ...
Obesity is a global health issue influenced primarily by genetic variants and environmental factors. This study aimed to examine the relationship between genetic and lifestyle factors and their interaction with obesity risk among university students. A total of 658 students from the same university participated in this study, including 531 females (mean age (SD): 21.6 (3.9) years) and 127 males (21.9 (4.6) years). Among them, 550 were classified as normal weight or underweight (456 females and 94 males), while 108 were identified as overweight or obese (75 females and 33 males). All the participants underwent anthropometric and genetic screening and completed lifestyle and sleep quality questionnaires. The polygenic risk score, based on seven genetic variants (ADCY3 rs11676272, CLOCK rs1801260, GPR61 rs41279738, FTO rs1421085, RP11-775H9.2 rs1296328, SLC22A3 rs9364554, and TFAP2B rs734597), explained 8.3% (p < 0.0001) of the variance in body mass index (BMI). On the other hand, lifestyle factors-such as meal frequency, frequency of overeating, nut consumption as a snack, eating without hunger, frequency of antibiotic use in the past year, symptoms of dysbiosis, years of physical activity, sleep duration, bedtime, ground coffee consumption frequency, and evening coffee consumption time-accounted for 7.8% (p < 0.0001) of the variance in BMI. The model based on gene-environment interactions contributed 15% (p < 0.0001) to BMI variance. This study revealed that individuals with a higher genetic predisposition, as defined by the seven polymorphic loci, are more susceptible to becoming overweight or obese under certain lifestyle conditions.
... Coffee is one of the most consumed beverages in the world. 9 Green coffee beans are rich in chlorogenic acid (CGA) and related compounds such as quinic acid, p-coumaric acid, and caffeic acid. The compounds are similar in green and roasted coffee; however, some of these compounds are lost during the roasting process. ...
Objective: This study aimed to evaluate the effects of decaffeinated green coffee extract (DGCE) supplementation on anthropometric indices, blood glucose, leptin, adiponectin, and neuropeptide Y (NPY) in breast cancer survivors with obesity. Method: A total of 44 breast cancer survivors with obesity aged between 18 and 70 years and with a mean body mass index (BMI) of 31.62 ± 4.97 kg m-2 participated in this double-blind randomized clinical trial. Eligible patients were randomized to the intervention (n = 22) and control (n = 22) groups. They received two 400 mg capsules of DGCE or two identical placebos daily for 12 weeks. Serum concentrations of leptin, adiponectin, NPY, fasting blood sugar, insulin, and homeostatic model assessment for insulin resistance (HOMA-IR) were measured at the baseline and after completion of the intervention. Also, weight, waist circumference, fat percentage, muscle percentage, and visceral fat were measured. Results: There were no significant differences in terms of changes of anthropometric indices and concentrations of leptin, adiponectin, NPY, and blood sugar between the two studied groups. Conclusion: Supplementation with DGCE in breast cancer survivors with obesity had no significant effect on anthropometric indices and blood glucose, leptin, adiponectin, and NPY levels.
... However, a recent meta-analysis of RCTs determined that caffeine consumption is associated with an average weight loss of <2 kg after 4 weeks [360]. Moreover, data from cross sectional and observational studies have suggested that increased caffeine intake is associated with less weight gain in the long-term [361], and may also be beneficial for the maintenance of weight loss [362]. ...
Metabolic demands of skeletal muscle are substantial and are characterized normally as highly flexible and with a large dynamic range. Skeletal muscle composition (e.g., fiber type and mitochondrial content) and metabolism (e.g., capacity to switch between fatty acid and glucose substrates) are altered in obesity, with some changes proceeding and some following the development of the disease. Nonetheless, there are marked interindividual differences in skeletal muscle composition and metabolism in obesity, some of which have been associated with obesity risk and weight loss capacity. In this review, we discuss related molecular mechanisms and how current and novel treatment strategies may enhance weight loss capacity, particularly in diet-resistant obesity.
... There are a number of researches stating that it is helpful for weight loss and maintenance [9,10]. However, these researches focus on the ability of caffeine to boost metabolism and increase energy expenditure [11,12]. In this manuscript, we review another beneficial role of caffeine for overweight subjects, which is the potential to inhibit enzymatic activity of SSAO [13]. ...
Obesity is a worldwide prevalent metabolic disorder that is associated with diabetes, among many other diseases. Bearing this in mind, prevention and treatment ways need to be improved. Notably, activity of the enzyme semicarbazide-sensitive amine oxidase (SSAO) is found to be elevated in overweight subjects. Moreover, SSAO inhibition has resulted in an increase of histamine activity in adipose tissue and the limitation of body fat. The current review aims to overview the risks of obesity, rationalize the molecular ways of SSAO activity, and outline the strategies of inhibiting upregulated enzyme levels. It describes the differences between SSAO inhibitors and advances the prospective agents. Based on evidence, caffeine is proposed as an effective, safe, and reliable choice to inhibit SSAO activity. Furthermore, the histamine in adipocytes has been associated with SSAO activity. Therefore, it is suggested as one of the key compounds to be studied for obesity management. To conclude, inhibiting SSAO may attenuate weight gain and prevent related diseases.
Obesity refers to the excessive accumulation of fat caused by a long-term imbalance between energy intake (EI) and energy expenditure (EE). Over recent years, obesity has become a major public health challenge. Caffeine is a natural product that has been demonstrated to exert anti-obesity effects; however, the mechanisms responsible for the effect of caffeine on weight loss have yet to be fully elucidated. Most obesity-related deaths are due to cardiovascular disease. Recent research has demonstrated that caffeine can reduce the risk of death from cardiovascular disease; thus, it can be hypothesized that caffeine may represent a new therapeutic agent for weight loss. In this review, we synthesize data arising from clinical and animal studies over the last decade and discuss the potential mechanisms by which caffeine may induce weight loss, focusing particularly on increasing energy consumption, suppressing appetite, altering lipid metabolism, and influencing the gut microbiota. Finally, we summarize the major challenges associated with caffeine and anti-obesity research and highlight possible directions for future research and development.
Between 2021 and 2023, the Scientific Council of Dietplus®, a group specialized in overweight and obesity management, conducted a clinical study on 170 volunteer subjects with a BMI > 29 Kg/m2 consecutively recruited. The Dietplus® program comprises nutritional education, intensive, personalized coaching, and consuming food supplements rich in plant derivatives. The aim of this study was to assess the effect of the Dietplus® program on biometric, behavioral, and biological parameters. A control group of 30 obese patients was followed for a similar 12-week period. Mean weight loss reached 9 ± 2.1 kg in the Dietplus® test group versus a 1 ± 0.1 kg weight gain in the control group. Excess weight loss reached 33 ± 13%, and fat mass loss was 7.6% (p < 0.001); waist circumference was reduced by 30%. Quality of Life, Nutriscore, and Prochaska di Clemente scale significantly improved (p < 0.001). Biological parameters showed substantial improvements in the carbohydrate profile and insulin resistance (HOMA index) and in the lipid profile with lower plasma triglyceride (p < 0.01) and VLDL (p < 0.01) concentrations. Inflammatory parameters (orosomucoid, ultrasensitive C-reactive protein, and PINI indices) were also substantially reduced. These results indicate a substantial benefit in subjects who followed the Dietplus® program. (Dietplus® 116 Rue Robert Bunsen, 57460 Behren-lès-Forbach, France is active in France Belgium and Spain. Plant Derived Food Supplements are produced in France). Indeed, improvements were observed in all biometric, behavioral, and metabolic parameters.
While the role of exercise in managing obesity has been suggested, little is known about the effect of caffeine supplementation in the exercise program on body mass index (BMI), body fat percentage (%BF), and cholesterol. This research compared the effect of aerobic exercise with and without caffeine on BMI, %BF, and cholesterol level in obese Asian women. Twenty-seven participants were randomly allocated into three groups, which were an aerobic exercise without caffeine (A; n = 9), an aerobic exercise with 3 mg/body weight—caffeine (AC; n = 9), and a control group (C; n = 9). The exercise was a 45-min exercise training at 60%–75% maximum heart rate conducted three times weekly for 8 weeks. The mixed-method repeated-measures analysis of variance was used to assess the effect of treatments and time (i.e., pretest and posttest) on the outcome measures, followed by simple effect analyses with Bonferroni correction. While there was a significant improvement in BMI and %BF from the pretest to posttest, this was superseded by a time-by-treatment interaction effect. For the time-by-treatment interaction, the cholesterol levels in the A and AC groups were significantly lower than in C, suggesting that the benefit of the exercise program is most evident in controlling cholesterol. In conclusion, the 3 mg/kg body weight caffeine does not appear to provide additional benefit in the 8-week moderate-intensity aerobic exercise session in improving BMI, %BF, and cholesterol among obese Asian women. Further research with higher caffeine dosage and larger and more heterogenous sample sizes is recommended to confirm the findings.
Obesity are defined as excessive fat accumulation caused of imbalance energy in and energy out. Consuming a cup of coffee can help prevent obesity through chlorogenic acid compound. Chlorogenic acid is one of biactive component that has an important role to our body. Chlorogenic acid has a potential role in body weight reduction and preventing obesity. Chlorogenic acid has an effect to inhibit the absorption of glucose in the intestine, block the conversion of glucose to fat in the adipose tissue and protect from weight gain. Chlorogenic acid that contain in coffee has a differences that depend on variety, type, roasting duration, temperature and coffee bean size. Based on several studies, giving chlorogenic acid as a form of supplementation or green coffee extract has demonstrated a consistent result. Those studies explain that chlorogenic acid in coffee can inhibit body fat accumulation and reducing body weight. The aim of this systematical review was to know the contain of chlorogenic acid in coffee and analyze the effect of giving chlorogenic acid to obesity. The experimental studies in human and animal subjects in the last 15 years as inclusion criteria and studies that is not represent the anthropometry result as exclusion criteria through electronic database were comprehensively reviewed. The result from five studies demonstrated that chlorogenic acid has an effect to reduce body weight, reduce body fat percentage, and reduce blood glucose concentration with the duration and chlorogenic acid dosage differently. Chlorogenic acid has many benefits in improving the obesity.
Combining an exercise and nutritional intervention is arguably the optimal method of creating energy imbalance for weight loss. This study sought to determine if combining exercise and caffeine supplementation was more effective for promoting acute energy deficits and manipulations to substrate metabolism than exercise alone. Fourteen recreationally-active participants (Mean ± SD BMI: 22.7 ± 2.6 kg∙m-2) completed a resting control trial (CON), a placebo exercise trial (EX), and a caffeine exercise trial (EX+CAF, 2x 3 mg∙kg-1 of caffeine 90 min before and 30 min after exercise) in a randomized, double-blinded design. Trials were 4 h in duration with 1 h of rest, 1 h of cycling at ~65 % power at VO2max or rest, and a 2 h recovery. Gas exchange, appetite perceptions, and blood samples were obtained periodically. Two hours after exercise, participants were offered an ad libitum test meal where energy and macronutrient intake were recorded. EX+CAF resulted in significantly greater energy expenditure and fat oxidation compared to EX (+250 kJ; +10.4 g) and CON (+3126 kJ; +29.7 g) (P < 0.05). A trend for reduced energy and fat intake compared to CON (-718 kJ; -8 g) (P = 0.055) was observed. Consequently, EX+CAF created a greater energy deficit (P < 0.05). Caffeine also led to exercise being perceived as less difficult and more enjoyable (P < 0.05). Combining caffeine with exercise creates a greater energy deficit and the implications of this protocol for weight loss or maintenance over longer time periods in overweight/obese populations require further investigation.
Objective:
Epidemiological evidence shows that chronic coffee consumption in humans is correlated with a lower incidence of type 2 diabetes mellitus. For the experimental exploration of the underlying mechanisms, this effect needs to be replicated in an animal model of type 2 diabetes with a short lifespan.
Design:
Male C57BL/6 mice consumed regular coffee or water ad libitum and the development of obesity and diabetes caused by high-fat diet (55% lipids, HFD) was observed from week 10 on for 35 weeks in comparison with mice feeding on a defined normal diet (9% lipids, ND).
Results:
The massive weight gain in HFD mice was dose-dependently retarded (P=0.034), the moderate weight gain in ND mice was abolished (P<0.001) by coffee consumption, probably because of a lower feeding efficiency. The consumption of fluid (water or coffee) was significantly diminished by HFD (P<0.001), resulting in a higher coffee exposure of ND mice. On week 21 intraperitoneal glucose tolerance tests (IPGTT) showed a dose-dependent faster decline of elevated glucose levels in coffee-consuming HFD mice (P=0.016), but not in ND mice. Remarkably, a spontaneous decrease in non-fasting glycaemia occurred after week 21 in all treatment groups (P<0.001). On week 39 the IPGTT showed diminished peak of glucose levels in coffee-consuming HFD mice (P<0.05). HFD mice were hyperinsulinaemic and had significantly (P<0.001) enlarged islets. Coffee consumption did not affect islet size or parameters of beta-cell apoptosis, proliferation and insulin granule content.
Conclusion:
Coffee consumption retarded weight gain and improved glucose tolerance in a mouse model of type 2 diabetes and corresponding controls. This gives rise to the expectation that further insight into the mechanism of the diabetes-preventive effect of coffee consumption in humans may be gained by this approach.
OBJECTIVE
Previous meta-analyses identified an inverse association of coffee consumption with the risk of type 2 diabetes. However, an updated meta-analysis is needed because new studies comparing the trends of association for caffeinated and decaffeinated coffee have since been published.RESEARCH DESIGN AND METHODS
PubMed and Embase were searched for cohort or nested case-control studies that assessed the relationship of coffee consumption and risk of type 2 diabetes from 1966 to February 2013. A restricted cubic spline random-effects model was used.RESULTSTwenty-eight prospective studies were included in the analysis, with 1,109,272 study participants and 45,335 cases of type 2 diabetes. The follow-up duration ranged from 10 months to 20 years. Compared with no or rare coffee consumption, the relative risk (RR; 95% CI) for diabetes was 0.92 (0.90-0.94), 0.85 (0.82-0.88), 0.79 (0.75-0.83), 0.75 (0.71-0.80), 0.71 (0.65-0.76), and 0.67 (0.61-0.74) for 1-6 cups/day, respectively. The RR of diabetes for a 1 cup/day increase was 0.91 (0.89-0.94) for caffeinated coffee consumption and 0.94 (0.91-0.98) for decaffeinated coffee consumption (P for difference = 0.17).CONCLUSIONS
Coffee consumption was inversely associated with the risk of type 2 diabetes in a dose-response manner. Both caffeinated and decaffeinated coffee was associated with reduced diabetes risk.
Coffee consumption has been shown to be associated with various health outcomes, but no comprehensive review and meta-analysis of the association between coffee consumption and total mortality has been conducted. To quantitatively assess this association, we conducted a meta-analysis of prospective cohort studies. Eligible studies were identified by searching the PubMed and EMBASE databases for all articles published through June 2013 and reviewing the reference lists of the retrieved articles. Pooled relative risks (RR) with 95 % CI were calculated using a random-effects model. We identified twenty studies of coffee consumption and total mortality, including 129 538 cases of deaths among the 973 904 participants. The RR of total mortality for the high v. low category of coffee consumption was 0·86 (95 % CI 0·80, 0·92). The pooled RR for studies using ≥ 2-4 cups/d as a cut-off for the high category was similar to that for studies using ≥ 5-9 cups/d as the cut-off. By geographical region, the inverse association tended to be stronger for the eight studies conducted in Europe (RR 0·78, 95 % CI 0·70, 0·88) and three studies carried out in Japan (RR 0·82, 95 % CI 0·73, 0·92) than for the nine studies conducted in the USA (RR 0·92, 95 % CI 0·84, 1·00). The inverse association was similar for men (RR 0·81, 95 % CI 0·73, 0·90) and women (RR 0·84, 95 % CI 0·79, 0·89). A weak, but significant, inverse association was found with moderate coffee consumption (1-2 cups/d; RR 0·92, 95 % CI 0·87, 0·98). High decaffeinated coffee consumption was also found to be associated with a lower risk of death, but the data are limited. Our findings indicate that coffee consumption is associated with a reduced risk of total mortality.
Single-dose oral administration of 100 mg caffeine increased the resting metabolic rate of both lean and postobese human volunteers by 3-4% (p less than 0.02) over 150 min and improved the defective diet-induced thermogenesis observed in the postobese subjects. Measurements of energy expenditure (EE) in a room respirometer indicate that repeated caffeine administration (100 mg) at 2-h intervals over a 12-h day period increased the EE of both subject groups by 8-11% (p less than 0.01) during that period but had no influence on the subsequent 12-h night EE. The net effect was a significant increase (p less than 0.02) in daily EE of 150 kcal in the lean volunteers and 79 kcal in the postobese subjects. Caffeine at commonly consumed doses can have a significant influence on energy balance and may promote thermogenesis in the treatment of obesity.
Physical inactivity is a global concern, but diverse physical activity measures in use prevent international comparisons. The International Physical Activity Questionnaire (IPAQ) was developed as an instrument for cross-national monitoring of physical activity and inactivity.
Between 1997 and 1998, an International Consensus Group developed four long and four short forms of the IPAQ instruments (administered by telephone interview or self-administration, with two alternate reference periods, either the "last 7 d" or a "usual week" of recalled physical activity). During 2000, 14 centers from 12 countries collected reliability and/or validity data on at least two of the eight IPAQ instruments. Test-retest repeatability was assessed within the same week. Concurrent (inter-method) validity was assessed at the same administration, and criterion IPAQ validity was assessed against the CSA (now MTI) accelerometer. Spearman's correlation coefficients are reported, based on the total reported physical activity.
Overall, the IPAQ questionnaires produced repeatable data (Spearman's rho clustered around 0.8), with comparable data from short and long forms. Criterion validity had a median rho of about 0.30, which was comparable to most other self-report validation studies. The "usual week" and "last 7 d" reference periods performed similarly, and the reliability of telephone administration was similar to the self-administered mode.
The IPAQ instruments have acceptable measurement properties, at least as good as other established self-reports. Considering the diverse samples in this study, IPAQ has reasonable measurement properties for monitoring population levels of physical activity among 18- to 65-yr-old adults in diverse settings. The short IPAQ form "last 7 d recall" is recommended for national monitoring and the long form for research requiring more detailed assessment.
Differences between successful long-term weight loss maintainers and the general population with regard to eating and weighing habits, non-normative eating behaviors, and eating-related and general psychopathological parameters are unknown.
Self-identified weight loss maintainers from the German Weight Control Registry (GWCR, n = 494) were compared with a representative sample of the general German population (n = 2,129). The samples did not differ in current BMI. Using the same assessment instruments in both cohorts, a variety of eating-related and psychological variables were determined.
The GWCR participants reported more self-weighing and higher eating frequency but less hot meal consumption and more eating-out-of-home. Binge eating, compensatory behaviors, and concerns about shape and weight were reported more often by successful weight loss maintainers. Scores of depression and worrying about health were slightly higher whereas severity of somatic symptoms was less pronounced in the GWCR participants.
Overall, our data suggest that successful weight loss maintainers are characterized by more concerns about shape and weight, greater binge eating frequency, and higher use of compensatory behaviors. The latter suggests that weight loss maintenance might not only be achieved by healthy strategies but also by non-normative behaviors which might increase the vulnerability for weight regain.
© 2015 The Obesity Society.
Coffee is the most widely consumed beverage in the United States (US) after water, and is the principal source of caffeine intake among adults. The biological effects of coffee may be substantial and are not limited to the actions of caffeine. Coffee is a complex beverage containing hundreds of biologically-active compounds, and the health effects of chronic coffee intake are wide ranging. From a cardiovascular (CV) standpoint, coffee consumption may reduce the risks of type 2 diabetes mellitus (T2DM) and hypertension (HTN), as well as other conditions associated with CV risk such as obesity and depression; but it may adversely affect lipid profiles depending on how the beverage is prepared. Regardless, a growing body of data suggests that habitual coffee consumption is neutral to beneficial regarding the risks for a variety of adverse CV outcomes including coronary heart disease (CHD), congestive heart failure (CHF), arrhythmias, and stroke. Moreover, large epidemiological studies suggest that regular coffee drinkers have reduced risks for mortality-both CV and all-cause. The potential benefits also include protection against neurodegenerative diseases, improved asthma control, and lower risk of select gastrointestinal diseases. A daily intake of about 2 to 3 cups of coffee appears to be safe and is associated with neutral to beneficial effects for most of the studied health outcomes. However, most of the data on coffee's health effects are based upon observational data, with very few randomized controlled studies, and association does not prove causation. Additionally, the possible advantages of regular coffee consumption have to be weighed against potential risks (which are mostly related to its high caffeine content) including anxiety, insomnia, tremulousness and palpitations, as well as bone loss and possibly increased risk of fractures.
To investigate the effects of different coffee amounts on dietary intake and appetite feelings in normal-weight and overweight/obese individuals.
Thirty-three volunteers (16 normal-weight, 17 overweight/obese) participated in three trials: they consumed a standard breakfast along with 200 ml of either coffee with 3 or 6 mg caffeine/kg body weight (Coffee 3 and Coffee 6, respectively), or water. At fasting and at standard time points for the 3 h following breakfast/drink consumption participants recorded their appetite feelings on visual analogue scales. At 180 min, participants consumed an ad libitum meal and the next day they recalled their food intake during the experimental day.
A significant intervention effect was found for the energy intake of the ad libitum meal (P = 0.05) and of the whole day (P = 0.02) only in overweight/obese individuals. Specifically, Coffee 6 resulted in a reduced energy intake during the ad libitum meal compared to Coffee 3 (P = 0.03) and in the total day compared to both water (P = 0.04) and Coffee 3 (P = 0.008). No effect was observed for the appetite feelings.
A moderate coffee amount can effectively reduce energy intake in the following meal and in the total day compared to lower or no coffee intake in overweight/obese participants.
To assess and to evaluate possible effects arising from Web-based data collection on the results of a study.
We analyzed participants of the German Weight Control Registry (GWCR) of whom 328 chose to use Web-based questionnaires and 139 preferred to participate via a traditional postal survey. Furthermore, we included data of 212 individuals sampled independently from the general population who fulfilled the study's inclusion criteria-giving us the chance to differentiate between response bias (concerning Web-based data collection) and general selection bias (concerning participation in the GWCR).
In addition to selection bias (GWCR participants are overall better educated, more likely to live in a partnership, more often female, and older than the general population), we also found a substantial response bias: Participants using the Internet were younger, better educated, and more often male compared with participants preferring the paper-and-pencil version. However, after adjusting for these differences, we found no additional direct effect of Web-based data collection on any of the outcome variables.
Web-based epidemiologic studies still do not attract the same participants as postal surveys, even in highly industrialized countries. However, after adjusting for this bias, the same results can be expected.