Critique 052: Does moderate alcohol consumption increase body weight? – 16 August 2011

Sayon-Orea C, Martinez-Gonzalez MA, Bes-Rastrollo M.  Alcohol consumption and body weight: a systematic review.  Nutrition Reviews 2011;69:419-431.

Authors’ Abstract

Based on the fact that energy content in 1 gram of alcohol is 29 kJ or 7.1 kcal, alcohol consumption can lead to weight gain.  The present review was conducted to analyze the effects of alcohol consumption on body weight.  A search of the Medline database for the period 1984 to March 2010 was conducted to identify cross-sectional, prospective cohort studies and intervention trials investigating the relationship between alcohol consumption and the risk of weight gain. Thirty-one publications were selected on the basis of relevance and quality of design and methods.

The findings from large cross-sectional studies as well as from well-powered, prospective, cohort studies with long periods of follow-up were contradictory. Findings from short-term experimental trials also did not show a clear trend. The overall results do not conclusively confirm a positive association between alcohol consumption and weight gain; however, positive findings between alcohol intake and weight gain have been reported, mainly from studies with data on higher levels of drinking.  

It is, therefore, possible that heavy drinkers may experience such an effect more commonly than light drinkers. Moreover, light-to-moderate alcohol intake, especially wine intake, may be more likely to protect against weight gain, whereas consumption of spirits has been positively associated with weight gain.  Further research should be directed towards assessing the specific roles of different types of alcoholic beverages.  Studies should also take the effect of consumption patterns into account.  In addition, a potential effect modifier that has not been evaluated before but might be important to consider is the subjects’ previous tendency to gain weight.

Forum Comments

Background:  As pointed out by the authors of this paper, obesity is becoming a rapidly increasing major health problem throughout the developed world.  While it is common for individuals, especially women, to state that they avoid all alcohol consumption because they “do not want to gain weight,” data are very limited on this subject.  There are beginning to appear reports suggesting that moderate drinking, especially of wine, is not associated with increasing body weight, while heavy drinking probably is.  Hence, this review article is very timely.

Many investigators, including Wannamethee et al1 and Tolstrup and colleagues,2 have found that the odds ratios for having a high BMI was lower among subjects drinking more frequently.  These authors concluded that for a given level of total alcohol intake, obesity was inversely associated with drinking frequency, whereas the amount of alcohol intake was positively associated with obesity.  These results suggest that the frequent consumption of small amounts of alcohol is the optimal drinking pattern associated with a lower risk of obesity.

It should be pointed out that the relation of alcohol intake to obesity is especially difficult to study in the population because, traditionally, most drinkers, especially heavy drinkers, have tended to also be smokers, and smoking is known to lower the risk of obesity.  The majority of papers included in the present review took smoking into account.  One well-done large study by Breslow and Smothers3 was limited to non-smokers and showed quite clearly that whereas drinking more per occasion was associated with increased weight, drinking small amounts of alcohol on a frequent basis was associated with lower body mass.  In that study, the highest risk of a high BMI was among abstainers.Another large cross-sectional study limited to non-smokers, by Arif and Rohrer,4 also found little effect of moderate drinking on weight.  The authors reached the following conclusions: the risk of obesity was lowest for (a) current drinkers; (b) drinkers reporting no binge drinking; (c) people averaging no more than 2 drinks/day; and (d) those who report an average of < 5 drinks/week.4

Comments on the present paper:  The paper by Sayon-Orea et al is a review of the topic, but does not include a formal meta-analysis of the effects of alcohol on body weight or obesity.  The review includes cross-sectional and prospective studies (and a few small intervention studies) among subjects who varied by age (adolescence to old age), culture (from Americans and Europeans to Asians), and principal type of beverage consumed and pattern of drinking.  Potentially important information missing from many of the studies reviewed includes data on previous weight gain or loss by the individual before he/she was included in the study, details related to “binge drinking,” and limited data on other dietary factors.

The authors recognize most of these limitations.  While they state that many of the studies they reviewed appear to be contradictory in their results, they do reach two major conclusions.  The first was “positive associations between alcohol and weight gain were mainly found in studies with data on higher levels of drinking; it is possible that an effect on weight gain or abdominal adiposity may only be experienced by heavy drinkers.”  A second conclusion of the authors was that “the type of alcoholic beverage might play an important role in modifying the effect of alcohol consumption on weight gain,” with more favorable effects generally seen among consumers of wine.

Need for a formal meta-analysis from prospective studies:  It would be assumed that, given that long-term intervention trials have not been done, the best source of information on the topic that is currently available is from prospective studies with long-term follow up.  Indeed, the present paper contains data from 13 prospective studies, of which 10 are rated “good,” and 9 of these are based on data from adult subjects in Europe or the USA.  These 9 studies contain more than 190,000 subjects, with all analyses adjusted for age and smoking (and most for other variables such as socio-economic level and baseline BMI).  They also have reasonable follow-up periods between 3 and 12.9 years (all but one study with at least 5 years of follow up).  It would appear that this is a quite homogenous group of studies that would be appropriate for a formal meta-analysis (with, for example, stratification of results by gender and by type of beverage).  Such a meta-analysis might provide rather precise estimates of effect of alcohol drinking on obesity for adults in Western industrialized societies. 

Are alcohol calories added to total calories or does alcohol replace other sources of calories?  It may seem surprising that we still do not know the extent to which the intake of alcohol affects total calorie intake.  In a paper from 1991, Colditz et al5 suggest that women substitute alcohol for sugar calories, while men add alcohol calories to their diet.  Suter et al6 state that most studies show that, for moderate drinkers, alcohol calories are added to food calories.  However, these authors add: “There is, however, one limitation to the latter epidemiologic finding.  The extent to which alcohol energy represents a usable source of energy (i.e., for adenosine triphosphate [ATP] production) and whether alcohol can be regarded as an energy source comparable to the other main energy substrates (i.e., fat and carbohydrates) are not known.”6

It should be mentioned that while beer, wine, and spirits all contain alcohol, the present study suggests that the effects on weight increase are greater for spirits than for other beverages.  Thus, as one Forum reviewer comments: “Does this suggest that the polyphenols in wine are associated with some protection against weight gain, whereas the antioxidant action of whisky and brandy, for example, is due mainly to the transition metal ions they contain?”  On the other hand, it is still possible that the spirits-drinking subjects in this study were just consuming more alcohol than were consumers of other beverages.

Other approaches for studying alcohol and body weight:  There have been a variety of other approaches for judging the relation of alcohol to weight and changes in weight.  An unusual contribution to this topic came from a study by Dixon et al7 on factors affecting weight loss after the surgical placement of a lap-band to induce weight loss.  These investigators report that following the insertion of such a band, “Patients who consumed alcohol regularly had a better rate of weight loss (R= 0.23, p<0.005) than did non-drinkers.”7

Alcohol, obesity, and metabolic factors:  It has been shown repeatedly that alcohol is inversely associated not only with obesity, but also with other components of the so-called metabolic syndrome and with the risk of developing diabetes.  Howard et al8 and Koppes et al9 have carried out meta-analyses of the association of alcohol consumption and the risk of developing diabetes: they show an approximately 30% decrease in risk for moderate drinkers.

The findings relating alcohol to metabolic syndrome show associations similar to those for diabetes.  In the NHLBI Family Heart Study, Djoussé et al10 reported an inverse association between alcohol consumption and the presence of the metabolic syndrome.  In NHANES III, Freiberg et al11 found that moderate drinking was associated with lower risk of most components of the metabolic syndrome (all components except for hypertension).  In a meta-analysis on alcohol intake and metabolic syndrome, based on data from seven previous studies with a total of 22,000 subjects, Alkerwi and coworkers12 found that the moderate intake of alcohol (defined as ≤40 g of alcohol per day for men and ≤20 g of alcohol per day for women) was associated with 16% lower risk of metabolic syndrome for men and 25% lower risk for women; no significant effects were seen for heavier drinking.12

In a study of metabolic factors among the severely obese, Dixon et al13 found that “Light-to-moderate alcohol consumption is associated with a lower prevalence of type 2 diabetes, reduced insulin resistance, and more favorable vascular risk profile in the severely obese.  We would propose that light to moderate alcohol consumption should not be discouraged in the severely obese.”13

Alcohol metabolism and potential effects on weight change in drinkers:  The metabolism of alcohol differs from that of other foods, in that approximately 90% of the alcohol that is absorbed into the blood is metabolized by oxidation pathways.  Oxidative metabolism occurs primarily in the liver, using three enzymes and pathways, each located in a different subcellular compartment of the liver.  They are as follows:  (1)  the enzyme alcohol dehydrogenase (ADH) breaks down alcohol to acetaldehyde which is then metabolised by the enzyme acetaldehyde dehydrogenase (ALDH) to acetic acid, which is then further metabolised to be used in cellular reactions.  (2)  Alcohol is also metabolised to acetaldehyde by the enzyme microsomal mixed function oxidase enzyme pathway.  This P450 2E1 enzyme pathway is a subset of the cytochrome P450 system that metabolises other drugs and foods.  (3)  Alcohol is also metabolized by a catalase enzyme, which is found throughout the body, including in the brain.

One Forum reviewer states: “I think that the most important difference between the metabolism of alcohol and other foods is (1) alcohol calories can not be stored in the body; and (2) almost all metabolism takes place in the liver, thus alcohol calories cannot be utilized by muscles for energy.”

Alcohol’s effects on thermogenesis:  A Forum member points out that the authors of the present paper do not mention an interesting factor in the development of protection against obesity: Non Exercise Activity Thermogenesis (NEAT).14  Humans show considerable inter-individual variation in susceptibility to weight gain in response to overeating; the activation of NEAT dissipates excess energy to preserve leanness and failure to activate NEAT may result in ready fat gain.15

An effect of alcohol on NEAT could be a possible explanation for the seemingly missing effect of alcohol calories on weight gain found in many studies.  The theory that alcohol may affect NEAT differently from other foods finds support from studies by Raben et al.16  These investigators have shown that diet-induced thermogenesis was larger after an alcohol meal (by 27%; P < 0.01), whereas protein produced an intermediary response (17%; NS) compared with carbohydrate and fat (meal effect: P < 0.01).  After the alcohol meal, fat oxidation and leptin concentrations were greatly suppressed.  These authors conclude that “Intake of an alcohol-rich meal stimulates energy expenditure but suppresses fat oxidation and leptin more than do isoenergetically dense meals rich in protein, carbohydrate, or fat.”16  Consideration of NEAT should be included in future studies of alcohol and obesity. 

References from Forum Comments

1.  Wannamethee SG, Field AE, Colditz GA, Rimm EB: Alcohol intake and 8-year weight gain in women: a prospective study, Obes Res 2004;12:1386-1396. 

2.  Tolstrup JS, Heitmann BL, Tjonneland AM, et al: The relation between drinking pattern and body mass index and waist and hip circumference, Int J Obes (Lond) 2005;29:490-497. 

3.  Breslow RA, Smothers BA.  Drinking patterns and body mass index in never smokers.  National Health Interview Survey, 1997–2001.  Am J Epidemiol 2005;161:368-376. 

4.  Arif AA, Rohrer JE.  Patterns of alcohol drinking and its association with obesity: data from the Third National Health and Nutrition Examination Survey, 1988-1994.  BMC Public Health 2005;5:126 [doi:10.1186/1471-2458-5-126].

5.  Colditz GA, Giovannucci E, Rimm EB, Stampfer MJ, Rosner B, Speizer FE, Gordis E, Willett WC.  Alcohol intake in relation to diet and obesity in women and men.  Am J Clin Nutr 1991;54:49-55.

6.  Suter PM, Hasler E, Vetter W.  Effects of alcohol on energy metabolism and body weight regulation: is alcohol a risk factor for obesity? Nutr Rev 1997;55:157–171.

7.  Dixon JB, Dixon ME, O’Brien PE.  Pre-operative predictors of weight loss at 1-year after LAP-BAND surgery.  Obes Surg 2001;11:200-207.

8.  Howard AA, Arnsten JH, Gourevitch MN: Effect of alcohol consumption on diabetes mellitus: a systematic review.  Ann Intern Med 2004;140:211-219.

9. Koppes LL, Dekker JM, Hendriks HF, et al: Moderate alcohol consumption lowers the risk of type 2 diabetes: a meta-analysis of prospective observational studies.  Diabetes Care 2005;28:719-725.

10.  Djoussé L, Arnett DK, Eckfeldt JH, Province MA, Singer MR, Ellison RC.  Alcohol consumption and metabolic syndrome in the NHLBI Family Heart Study: Does the type of beverage matter?  Obes Res 2004;12:1375-1385.

11. Freiberg MS, Cabral HJ, Heeren TC, Vasan RS, Ellison RC.  Alcohol consumption and the prevalence of the Metabolic Syndrome in the US: a cross-sectional analysis of data from the Third National Health and Nutrition Examination Survey.  Diabetes Care 2004;27:2954-2959.

12.  Alkerwi A, Boutsen M, Vaillant M, Barre J, Lair ML, Albert A, Guillaume M, Dramaix M.  Alcohol consumption and the prevalence of metabolic syndrome: a meta-analysis of observational studies.  Atherosclerosis 2009;204:624-635.

13.  Dixon JB, Dixon ME, O’Brien PE.  Alcohol consumption in the severely obese: relationship with the metabolic syndrome.  Obes Res 2002;10:245-252.

14.  Levine JA.  Nonexercise activity thermogenesis (NEAT): environment and biology.  Am J Physiol Endocrinol Metab 2004;286:E675–E685.

15.  Levine JA, Eberhardt NL, Jensen MD.  Role of Nonexercise Activity Thermogenesis in resistance to fat gain in humans.  Science 1999;283:211-214.

16.  Raben A, Agerholm-Larsen L, Flint A, Holst JJ, Astrup A.  Meals with similar energy densities but rich in protein, fat, carbohydrate, or alcohol have different effects on energy expenditure and substrate metabolism but not on appetite and energy intake.  Am J Clin Nutr 2003;77:91-100.

Forum Summary

A paper from Spain provides an extensive review of the association between alcohol consumption and body weight.  It includes descriptions of cross-sectional and prospective studies (and a few small intervention studies) among subjects who varied in age (adolescence to old age), culture (from Americans and Europeans to Asians), and principal type of beverage consumed and pattern of drinking.  The authors state that many of the studies they reviewed appear to be contradictory in their results.  However, based on their review, they conclude that “as positive associations between alcohol and weight gain were mainly found in studies with data on higher levels of drinking, it is possible that an effect on weight gain or abdominal adiposity may only be experienced by heavy drinkers.”  A second conclusion of the authors is that “the type of alcoholic beverage might play an important role in modifying the effect of alcohol consumption on weight gain,” with more favorable effects generally seen among consumers of wine.  A formal meta-analysis is not provided.  Forum members were uncertain whether the higher risk seen for spirits drinkers in this study was due to the beverage they chose or to their consumption of larger amounts of alcohol.

The overall conclusions of the authors is that it is currently unclear whether alcohol consumption a risk factor for weight gain, but if so it appears to occur mainly among heavier drinkers.  They also state that “light-to-moderate alcohol intake, especially of wine, may be more likely to protect against, rather than promote, weight gain.”

Forum reviewers agreed with most of the conclusions of the authors, especially that current data do not clearly indicate if moderate drinking increases weight; further, the biologic mechanisms relating alcohol to changes in body weight are not well understood.  The Forum review comments on the strong protective effects of moderate drinking on the risk of metabolic syndrome and diabetes, both of which relate to increasing obesity.  And some studies suggest that even very obese people may be at lower risk of diabetes if they are moderate drinkers.  Forum members also reviewed some of the distinctive mechanisms by which alcohol is metabolized in the body (it provides calories that are rapidly absorbed and are not stored in fat) that could explain differences in the effects of calories from alcohol and from other foods. 

Forum members agree with the authors of this paper that future research efforts should be directed towards assessing the specific roles of different types of alcoholic beverages, taking into account drinking patterns, and perhaps including in the analysis the propensity of individual subjects to gain weight in the past.  For now, there is little evidence that someone consuming small to moderate amounts of alcohol on a regular basis is increasing his or her risk of becoming obese. 

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Contributions to this critique from the International Scientific Forum on Alcohol Research were made by the following Forum members:

Erik Skovenborg, MD, Scandinavian Medical Alcohol Board, Practitioner, Aarhus, Denmark.

Creina Stockley, clinical pharmacology, Health and Regulatory Information Manager, Australian Wine Research Institute, Glen Osmond, South Australia, Australia.

Harvey Finkel, MD, Hematology/Oncology, Boston University Medical Center, Boston, MA, USA.

Arne Svilaas, MD, PhD, general practice and lipidology, Oslo University Hospital, Oslo, Norway.

Lynn Gretkowski, MD, Obstetrics/Gynecology, Mountainview, CA, Stanford University, Stanford, CA, USA.

Gordon Troup, MSc, DSc, School of Physics, Monash University, Victoria, Australia.

R. Curtis Ellison, MD, Section of Preventive Medicine & Epidemiology, Boston University School of Medicine, Boston, MA, USA.

Andrew L. Waterhouse, PhD, Marvin Sands Professor, Department of Viticulture and Enology, University of California, Davis, USA.