The association between alcohol intake and obesity in a sample of the Irish adult population, a cross-sectional study
The obesity epidemic is one of the most serious public health challenges of the twenty-first century. Alcohol has been studied as a possible risk factor for obesity, but the evidence is discordant.
This study examined the association between alcohol consumption and obesity in a sample of the Irish adult population.
An analytical cross-sectional study was conducted using secondary data from the 2017 Healthy Ireland Survey.
The primary survey recruited patients using a two-stage probability-based technique and a face-to-face-administered questionnaire to collect data.
Descriptive and comparative data were analysed to identify associations between alcohol-related variables with waist circumference (WC) and body mass index (BMI). Regression analysis was performed to examine the associations between harmful alcohol consumption (AUDIT-C score ≥ 5) (exposure variable) and obesity indicators (WC and BMI), the primary outcomes of interest.
Adjustments were made for sociodemographic, health-related, and other alcohol-related variables.
A total of 6864 participants, aged 25 and older, took part in this survey (response rate = 60.4%). Most of the participants (81.9%) were alcohol consumers, with the majority consuming alcohol less than three times per week (76.3%); 47.7% were considered heavy alcohol users (AUDIT-C score ≥ 5).
After controlling for possible confounders, positive associations of heavy alcohol consumption with WC (β = 1.72) and BMI (OR = 1.47) were observed.
Binge alcohol use was positively associated with WC (β = 1.71), while alcohol consumption frequency was significantly and inversely associated with BMI (OR = 0.59).
Heavy alcohol use was associated with obesity (high BMI, large WC) after controlling for possible confounders.
Frequent binge alcohol users were more likely to have a large WC, while frequent alcohol consumers were less likely to have obesity.
Further longitudinal studies to examine the exact association between alcohol consumption and obesity are warranted.
Heavy alcohol consumption and obesity
The current study showed positive associations between heavy alcohol consumption (AUDIT-C score ≥ 5) and obesity indicators (both BMI and WC) after controlling for sociodemographic and health related variables.
After controlling for binge alcohol use and alcohol consumption frequency, heavy alcohol consumption continued to be significantly associated with WC and overweight/obesity (BMI ≥ 25 kg/m2).
No other study has employed the AUDIT-C questionnaire to investigate the association between alcohol consumption and obesity. Using the AUDIT-C can help eliminate inconsistencies in the evaluation of the association between alcohol use and obesity.
The exact underlying mechanism through which alcohol consumption is associated with obesity is not fully understood. According to the existing literature, alcohol consumption is the second-highest source of energy, providing almost 29 kJ (7 kcal) of energy. It has been found to have an additive effect on energy obtained from other non-alcoholic sources, which can lead to weight gain.
Additionally, alcohol is a suppressant of fat oxidation, favours lipid storage, and acts as a precursor for fat synthesis.
Furthermore, alcohol intake enhances cortisol secretion, which subsequently affects the distribution pattern of fat in the body.
Binge alcohol use has a catabolic effect on muscle tissue, leading to fat deposition in visceral organs and muscles, which further leads to the development of various noncommunicable diseases, including obesity and diabetes mellitus.
Frequency of alcohol consumption and obesity
The current study showed an inverse association between frequency of alcohol consumption and overweight/obesity (BMI ≥ 25.0 kg/m2); with frequent alcohol consumers (≥ 3 times a week) being 49% less likely to be affected by overweight/obesity. However, no significant association was found between frequency of alcohol consumption and WC.
Previous studies examined the association between alcohol frequency and obesity, and the results were discordant. Some studies found inverse associations between the frequency of alcohol consumption (using a one-year recall period) and obesity indicators (BMI and WC) in both sexes. A study in Scotland and England, on the other hand, found a bell-shaped association between the frequency of alcohol consumption (using a 7-day recall period) and obesity indicators (BMI, WHR), with no difference in risk observed between those who never consumed alcohol and those who consumed alcohol the most frequently.
Another study, which used a 24-hour recall period, on Korean adults aged 40 to 60, found no significant association between the frequency of alcohol consumption and obesity (WC). However, this lack of an association could be related to the lower prevalence of abdominal obesity in the study population, < 8% in both sexes; thus, an exact association might be difficult to obtain.
Several factors could explain the inverse association between alcohol frequency and obesity.
- First, alcohol intake might affect macronutrient absorption, leading to reduced energy intake.
- Furthermore, alcohol consumption may stimulate thermogenesis by activating the ethanol oxidizing system, which can result in weight loss. This effect may be balanced by the various metabolic changes caused by alcohol consumption as well as the additional energy obtained from alcohol consumption. As a result, alcohol consumption frequency may not be directly associated with body weight or fat accumulation; rather, high alcohol consumption above the sex threshold may have an effect on abdominal obesity.
- Overall, based on existing research, encouraging alcohol use to lower the risk of obesity is not recommended, given that the precise mechanism is not fully understood.
Binge alcohol use and obesity
Nearly one-third (32.1%) of the study population engaged in binge alcohol use. Univariate analysis revealed a significant association between binge alcohol use and obesity indicators (both BMI and WC).
After controlling for sociodemographic, health-related, and other alcohol-related variables, the results revealed that frequent binge alcohol use (≥ 1 time per week) was significantly associated with a larger mean WC than less frequent binge alcohol use.
However, no significant association was found between binge alcohol use and overweight/ obesity.
Several studies have found a positive association between binge alcohol use and obesity, with individuals engaged in binge alcohol use being more likely to have a larger waist circumference or suffer from obesity (BMI).
However, a study conducted in the US using self-reported data on adults aged 18 with low income status did not find significant association, possibly due to the small sample size.
The reason for the positive association between binge alcohol use and obesity could be attributed to the presence of other impulsive behaviours, e.g., binge eating or abnormal eating patterns, which could confound the association between binge alcohol use and obesity.
Explanation for conflicting results in the association between alcohol consumption and obesity
Several factors could have contributed to the inconsistent results of the alcohol-obesity association.
- First, the underlying cause of obesity is complex, with several factors contributing to its development; however, not all of these characteristics have been researched or controlled for when assessing the association between alcohol consumption and obesity, which may bias the estimated association. The current study controlled for sociodemographic and health-related variables that could potentially confound the association between alcohol consumption and obesity. However, it did not investigate individual consumption patterns or the cultural dynamics that drive alcohol consumption, or the forms of legislation that could influence alcohol consumption.
- Second, epidemiological studies have examined the association between alcohol consumption and obesity using different instruments, making comparisons among studies difficult as no single well-established method was used to measure alcohol consumption. The window period used to recall alcohol intake varied between studies, ranging from a 24-hour recall period to a 7-day recall period, to a 12-month recall period. However, a short-term recall period does not account for the usual alcohol consumption patterns of individuals, the context in which individuals consume alcohol, or the influence of different seasons on alcohol consumption. The current study used a 12-month recall period to examine the association between alcohol consumption and obesity, which is considered more accurate in measuring the usual consumption trends in individuals.
- Third, the baseline prevalence of both alcohol consumption and obesity in a study population can also contribute to inconsistencies in the results obtained when analysing this association.
- Fourth, the types of alcoholic beverages might also affect the life habits of individuals, including eating patterns and physical activity, subsequently affecting body weight. Those who consume beer tend to have worse dietary habits than those who consume other alcoholic beverages. A US study showed that individuals who consumed beer tended to eat fewer fruits, vegetables, and grains than those who consumed wine and were more likely to eat ready-made food. Beer consumption was found to be positively associated with smoking, and the interaction of these factors might alter the effect of smoking on body weight. A study showed that current smokers who were heavy alcohol users (> 60 g/day) had a lower BMI than never smokers/former smokers. On the other hand, WC was largest among smokers with heavy lifetime alcohol consumption.
- Last, most of the studies used a self-report questionnaire to collect data; however, self-report questionnaires are prone to several types of bias (nonresponse bias, recall bias, and social desirability bias), and the results may be affected by intentional and unintentional misinterpretations of the questions being asked. One study found that self-reported alcohol intake accounted for only 40–60% of total sales, clearly underestimating the real amount of alcohol consumed. Specifically, heavy alcohol users tend to underreport their alcohol intake. The period for recall can also affect the accuracy of self-reported data. However, the data used in the current study were collected during face-to-face interviews that were conducted by trained staff with the aid of CAPI to minimize errors that might occur during the interview. However, a 12-month recall period can lead to recall bias, which cannot be avoided in studies with such a design.
As both alcohol consumption and obesity are prevalent in Ireland, this study has several implications.
- First, given that obesity is multifactorial in origin, existing national and international guidelines for obesity management have not addressed the possible association between alcohol consumption and obesity; rather, they have given general behavioural recommendations on alcohol consumption. This is partly because of the conflicting evidence regarding the association between alcohol consumption (both quantity and frequency) and obesity. More elucidation on the association between the consumption of alcohol and obesity is advocated in both national and international guidelines.
- Second, alcohol consumption is a significant public health problem in Ireland, with one-third of participants engaging in binge alcohol use and more than half engaging in heavy alcohol consumption. Despite current legislation to reduce alcohol use, the prevalence of heavy alcohol consumption is still high, partly due to the normative view of alcohol consumption in Ireland. To mitigate the burden of alcohol use, a multisectoral approach is recommended, including raising awareness of the negative psychological and physical effects, improving the capacity to recognize and treat alcohol use disorders, and raising public awareness of the possible association between alcohol consumption and obesity. Furthermore, the Alcohol Act, which was introduced in Ireland in 2018, included policies that can mitigate and further denormalize alcohol consumption, such as minimum unit pricing, structural separation, health labelling on alcohol-containing products, restrictions on alcohol advertising and marketing, regulation of alcohol sponsorship, and restrictions on certain promotional activities.
- Third, a more consistent methodology for examining the potential association between alcohol consumption and obesity is required to reduce inconsistency in the results obtained. A prospective study design is better for examining temporal sequences and reverse causation than a cross-sectional design, where such relationships cannot be revealed. The baseline prevalence of obesity and alcohol consumption in the study population is important to consider, as it may alter the overall association. The measurement of exposure should be standardised to improve generalizability and consistency of results. The current study was unique in that it assessed the relationship between alcohol use and obesity using the AUDIT-C questionnaire, which can eliminate inconsistencies in the results obtained. Personal interviews are also preferable to self-report questionnaires because they provide more accurate, complete, and high-quality data. The alcohol intake recall period should be long enough to accurately predict the pattern of alcohol consumption and account for periods where alcohol intake is high.
- Last, investment in research on alcohol consumption and obesity is recommended, particularly in Ireland, where both are considered public health problems. This will provide a better understanding of the association between alcohol consumption and obesity, as well as refine future recommendations for alcohol consumption in a community with a high prevalence of obesity. It is also recommended to tailor alcohol consumption guidelines based on an individual’s medical history.