To evaluate the effects of alcohol consumption, controlled for the energy in alcohol and chronic effects of smoking, on resting energy expenditure (REE) in college-aged female social drinkers.

1. Understand and give written consent
2. female between the ages of 21 and 35
3. moderate smokers, > or equal to 15 cigarettes/d
4. moderate drinkers, drinking about 3 and 10 drinks /wk, determined by the Michigan
5. Alcoholism Screening Test (MAST) short form

1. Refusal to consent
2. Pregnant women, or those who suspected they were pregnant
3. those who obtained a high score on the MAST
4. females on other drugs
5. those with a history of mental illness
6. subjects for whom alcohol or smoking would present an increased health risk
7. inappropriate amounts of cigarettes, indicated by inordinately low carbon monoxide concentrations (<10 ppm)

The four conditions in this within-subjects design consisted of 1) smoke 2 cigarettes and consume 29 mL pure grain alcohol in grapefruit juice, 2) only the 29 ml alcohol in grapefruit juice, 3) smoke 2 cigarettes and drink 207 mL cranberry juice [1054 kJ = 252 kcal], and 4) 2 cigarettes alone.

A random numbers table was used to determine the order of conditions for each subject.  Subjects were scheduled for 4 afternoon or evening time periods lasting ~ 3 h each.

“Steady state”- not discussed

ANTHROPOMETRIC:

Ht measured ? yes

Wt measured ? yes

Lean body mass? Not discussed

Clinical:

Monitored heart rate? Not discussed

Body temperature? Not discussed

Medications administered? not discussed

Resting energy expenditure:

IC type: canopy collection apparatus

Equipment of Calibration:  not discussed

Coefficient of variation using std gases:  not discussed

Rest before measure: not discussed

Measurement length: initial REE was a 25-min baseline; the second 105-min test provided an after-treatment measure

Steady state:

Not discussed

Fasting length: abstain from food 6 h prior to appointment; abstain from alcohol 24 h prior; abstain from smoking 2 h prior; and abstain from caffeine 2 h prior

Exercise restrictions: not discussed

Room temp:  not discussed

No. of measures within the measurement period:  1 25-minute continuous measure at baseline and the second 105-min continuous after-treatment measure.

Were some measures eliminated? First 5 min of each metabolic test was eliminated

Were a set of measurements averaged? Baseline 20 min (4) for that day was treated as one block and the second REE was divided into 10-min blocks of REE

Coefficient of variation in subjects measures?  not discussed

Training of measurer? not discussed

Subject training of measuring process?  not discussed; likely with first 5 minute elimination/adaptation

Dietary---no special dietary treatment

Intervening factor:  physical activity was not assessed

MEASUREMENT TIMING:

Sleep or rest—quietly resting; tapped and asked to raise a finger every 5 min to ensure that subjects remained

Statistical tests

Within-subjects multivariate analysis of variance (MANOVA) and a repeated-measures MANOVA; Dunnett’s multiple-comparison procedure;  P<0.05 was established as significant.

Outcome(s) and other measures

1. Dependent variables: IC-measured VO2 (ml/min), VCO2 (ml/min),RQ & RM(kcal/d).

2. Independent variables of gender height, weight

3. Smoking and alcohol nonconsumption were assessed before baseline tests by carbon monoxide and breathalyzer measures.

Blinding used: Yes; by use of grapefruit juice to mask the taste of alcohol.

N = 16 females

3 eliminated d/t inordinately low carbon monoxide concentrations (< 10 ppm, indicating that they were not moderate smokers (i.e., > or equal to 15/cigarettes/d)

N=13

Age range, y: 23-35

Mean age, y:  28.8 +/-3.67 y

Mean Cigarettes smoked/day, n: 22.5 +/- 5.9 (range 15-30)

Mean alcoholic drinks, n:  5.7 +/- 2.87 (range 3-10)

Mean carbon monoxide conc, ppm:   23 +/- 10.6 (range 16.5-40.25 ppm)

Mostly white women

ANTHROPOMETRIC

Interaction between time and treatment was significant (p<0.0001), as well as a significant effect between treatments (p<0.01).

Analyses indicated that alcohol significantly (p <0.05) increased REE for 55 min after administration and again from 76 to 85 min after administration.

Similarly, in the alcohol + smoking condition, the REE increased significantly (p <0.05) from baseline for 45 min after administration and again 76-95 min after administration. Although mean values were higher than baseline from 45 to 75 min, these differences were not significant.

Smoking + isoenergetic food load condition did not show significant (P>0.05)increases in REE above baseline; the effects of alcohol on REE were not related to the energy content of the alcoholic drink.

Within the smoking only condition, there were no significant differences between any time period and baseline, indicating that smoking had no significant effects on the REE of these subjects (P>0.05). 

In conclusion, analyses indicated that alcohol significantly (p <0.05) increased REE for up to 95 min after ingestion [increases of 29.6 – 68.4 kJ or 124 – 287 kcal/24h], increases that could not be accounted for by the energy content of the drink alone. Smoking and alcohol together also raised REE above baseline but not more than alcohol alone.

Author’s Conclusions:

As stated by the author in body of report:

“The results of this investigation indicate that alcohol significantly increased metabolic rate in a sample of young women social drinkers. Both alcohol conditions significantly increased REE for most of the evaluation session. This increase in REE was not attributable to the potential thermic effects of the energy in the drink because the increases were greater than the isoenergetic food-load condition.

“The increase in REE observed after alcohol administration was not attributable to the potential confounding of smoking, given that many consumers of alcohol also smoke, because the smoking + alcohol condition did not increase REE more than did the alcohol-alone condition. If anything, smoking tended to blunt the thermic effects of alcohol.

“The findings are also consistent with initial studies reporting that alcohol increases REE.

“The current investigation is consistent with another recent study that suggests that energy wastage occurs even among healthy, young, social drinkers, and it appears that elevated metabolic rate is the mechanism of action for this excess energy expenditure.”

“Most studies find a significant increase in metabolic rate after food ingestion. However, the current food load, the energy equivalent of that found in the alcohol condition, was lower than is typically given in food studies and was in the form of simple carbohydrate, which typically does not produce as great of a thermic effect as other preloads.

Although the literature generally suggests that smoking increases metabolic rate, smoking two cigarettes after a 2-h abstinence probably is insufficient to produce sustained increases in metabolic rate.  There may be individual differences in metabolic rate, with some subjects not increasing, or even decreasing, metabolic rate as a function of smoking. Given that all subjects received all experimental procedures in the current study, the lack of consistent increase in the smoking and isoenergetic food-load condition serves to strengthen one’s confidence in the consistent pattern that alcohol increased metabolic rate among these subjects.”

“The results should nonetheless be viewed with some degree of caution. . . the current study used only women because the effects of alcohol on body weight are much greater in women relative to men. [and is unknown if] results will fully generalize to men. 

Additionally, . . . given the consistent observation that black women have higher rates of obesity than white women, the current findings [of white women] need to be extended to determine whether the effects replicate among various populations at risk for obesity.  

The research design would have been stronger had it included an isoenergetic-replacement-only treatment.  Addition of juice to the alcohol is not an optimal method of assessing the “pure” thermic effect of alcohol. However, the potential compromise was weighed against the desire to have subjects blinded to treatment condition. Given that both juices were identical in energy content, one can readily infer the thermic effect of alcohol.

[Another limitation is the] current study evaluated the metabolic effects of alcohol as a result of ingesting approximately two drinks.

“In summary, alcohol increased metabolic rate in a sample of young, nonalcoholic, healthy women."

Strengths:

Randomized treatments

Limitations:

Small sample size

? generalizability; sample consisted of young, white women and nonalcoholics; may not be generalizable to men, older women or women of different ethnic backgrounds or chronic alcoholics

Alcohol commonly consumed with a meal (mixture of carbohydrate, protein and fat) rather than a beverage (simple carbohydrates); not known what effect of alcohol on REE would be with a meal

Accuracy of IC techniques such as machine machine calibration, steady state, and rest before measure were not addressed and may effect RMR measure

Physical activity of subjects not addressed