The effect of ethanol on fat storage in healthy subjects

Ethanol exerts acute protein-sparing effects during postabsorptive but not during anabolic conditions in man

Ethanol abuse is frequently associated with protein malnutrition. To assess the acute effects of ethanol on whole-body protein metabolism, [1-13C]leucine kinetics were measured in eight postabsorptive normal male subjects three times, ie, during administration of two doses of ethanol (dose 1, 0.52 g/kg during 2 hours and 0.3 g/kg during 3 hours; dose 2, 0.69 g/kg during 2 hours and 0.3 g/kg during 3 hours) and during saline (controls). During the last 2 hours of the studies, glucose, insulin, and amino acids were infused to assess the effects of ethanol on protein kinetics under anabolic conditions (euglycemic clamp). The decreases in leucine flux (reflecting whole-body protein breakdown) and nonoxidative leucine disappearance (a parameter of protein synthesis) during saline infusion were abolished in both ethanol protocols (P < .05 or less v saline). The rate of leucine oxidation decreased during the higher dose of ethanol compared with saline (P < .005), indicating an anticatabolic effect. During anabolic conditions (clamp), leucine flux and nonoxidative leucine disappearance were significantly higher in both ethanol studies compared with saline (P < .05). Resting energy expenditure (REE) and oxygen consumption (VO2) during the euglycemic clamp increased to a greater degree during both ethanol studies than during saline (P < .05 or less). Thus, an elevation of blood ethanol concentrations to the levels observed in social drinking results in a net anticatabolic effect (diminished leucine oxidation) when ethanol is administered alone. However, during administration of other nutritional substrates, the anticatabolic effect was not detectable, possibly because ethanol enhanced nutrient-induced thermogenesis.

Carbohydrates and energy balance

In the early 1970s carbohydrates (CHOs) were believed to induce overconsumption and excess fat deposition. They are now perceived to protect against these consequences. This paper evaluates the evidence for this change of interpretation by considering (1) the energy content of CHOs, (2) the energetic efficiency with which they are handled by the body, and (3) their effects on appetite, relative to other macronutrients. CHOs are the least energy-dense macronutrients (delta Hc) and exhibit the greatest variability in digestibility. Doubling the usual levels of nonstarch polysaccharides (fiber) may decrease digestibility of a Western diet by 5%. De novo lipogenesis from dietary CHO is energetically inefficient but very limited on Western diets, which are relatively high in fat. There appears to be a hierarchy (protein > CHO > fat) in the extent to which the stores of the macronutrients are autoregulated by oxidation. Excess CHO intake tends to promote storage (but not de novo synthesis) of fat. The thermogenic effects of CHO are therefore relatively limited on Western diets. Per MJ of energy ingested, macronutrients differentially affect satiety (protein > CHO > fat) under conditions where fat is disproportionately energy dense. Isoenergetically dense loads of fat and CHO exert less pronounced differences on satiety. Under some conditions HC diets promote excess energy intakes. There is little evidence that a CHO-rich diet, or one with intense sweeteners, promotes spontaneous weight loss.

Effects of alcohol on energy metabolism and body weight regulation: is alcohol a risk factor for obesity?

Some studies have suggested that drinking in moderation may be beneficial for health, but many of these studies do not address body weight. Evidence suggests that consuming moderate amounts of alcohol is a risk factor for obesity, which is a risk factor for several adverse health outcomes. Recommendations regarding alcohol intake thus should take into account a variety of factors, including baseline body weight, location of body fat, and overall diet.

Influence of moderate daily wine consumption on body weight regulation and metabolism in healthy free-living males

OBJECTIVE

Although previous studies have clearly demonstrated that energy from alcohol may not be efficiently utilized to maintain body weight when it comprises 20% or more of the daily caloric intake, there is considerable debate regarding the influence of moderate alcohol consumption (< or = 5% of the total daily caloric intake) upon metabolism, substrate utilization and body weight regulation. Consequently, the objectives of this study were to determine whether moderate alcohol consumption could influence body weight via changes in substrate utilization, oxygen consumption or alterations in dietary macronutrient content.

METHODS

Fourteen male subjects (mean age = 32.1 years) participated in a 12-week, free-living, crossover trial in which they either drank red wine (270 ml; 13% v/v ethanol) daily for 6 weeks and then abstained for the next 6 weeks or vice-versa.

RESULTS

Whether wine was imbibed or not, no significant differences (p > 0.05) were demonstrated for any of the following variables: body weight, body fat percentage, skinfold thickness, resting metabolic rate, respiratory quotient, caloric intake, dietary macronutrient content, or fasting insulin or glucose concentrations.

CONCLUSIONS

In free-living subjects over a 6-week period, the addition of two glasses of red wine to the evening meal does not appear to influence any measured variable which may adversely affect body weight or promote the development of obesity during this time period.

Alcohol consumption: a risk factor for abdominal fat accumulation in men

An increased abdominal fat mass is regarded as an independent cardiovascular risk factor. In this cross-sectional study of 1099 men we found a significant positive association between alcohol intake and the waist/hip (W/H) ratio, an index for the abdominal fat mass. This relationship was independent of age and body weight. The results suggest that the risk of abdominal fat deposition could be minimized by a reduction of alcohol intake.

Short-term effects of alcohol consumption on appetite and energy intake

The relationship between alcohol intake and obesity remains uncertain. Evidence suggesting that alcohol-derived energy may be unregulated points to an inability to maintain appetite, energy balance and, hence, body weight when alcohol is introduced to the diet. This study investigated the short-term effects of alcohol on hunger and energy intake in 20 lean women. On 4 occasions, subjects were given a randomised preload drink ('alcohol', 'no alcohol', 'carbohydrate', 'water') followed by visual analogue scales (VAS) rating hunger and an ad lib test meal. There was no difference in hunger ratings (p > 0.05) nor in the amount of energy consumed during the test meal (F = 1.66, p > 0.05) following any of the 4 preloads. Consumption of the 2 high energy preload drinks ('alcohol', 0.91 MJ; 'CHO', 0.72 MJ) did not result in a compensatory decrease in the amount of energy subsequently eaten (ad lib intake: 'alcohol' = 2.62 MJ, 0.32 SEM; 'no alcohol' = 2.98 MJ, 0.28 SEM; 'CHO' = 2.93 MJ, 0.21 SEM; 'water' = 2.82 MJ, 0.25 SEM), suggesting either no physiological recognition or no regulation of energy consumed within a drink in quantities of less than 1 MJ. The addition of either alcoholic or CHO-containing carbonated beverages into the diet will result, in the short-term, to an overall increase in energy intake.

Effects of ethanol consumption on brown adipose tissue thermogenic capacity in mice

The objective of this work was to evaluate the effects of ethanol consumption on brown adipose tissue (BAT) thermogenic capacity in mice. Mice offered only ethanol (10%; v/v) for 10 days as drinking fluid had significant reductions in total energy and fluid intakes relative to mice given water, but net weight gains were similar. BAT thermogenic capacity was reduced in mice drinking ethanol, as shown by decreases in tissue protein and succinate dehydrogenase (SDH) activity and in the uncoupling protein content of isolated mitochondria. Ethanol consumption differed greatly between mice offered a choice between ethanol and water for 25 days after a 10-day habituation period, with only ethanol as the drinking solution. Total energy intake of mice that continue to consume the most ethanol voluntarily (up to 25% of total fluid intake) was significantly reduced but carcass fat was increased, relative to mice consuming less or no ethanol. Brown fat thermogenic capacity was not significantly affected by the degree of ethanol consumption. Basal and norepinephrine-stimulated rates of oxygen uptake of isolated brown adipocytes were not affected by ethanol. Thus, changes in the animal capacity for energy expenditure in brown adipose tissue does not appear an important factor to explain the effects of ethanol consumption on fat deposition in mice.

Acute thermogenic effects of nicotine and alcohol in healthy male and female smokers

Nicotine intake is associated with lower body weight in both women and men. Despite its energy content, alcohol consumption is also associated with lower body weight in women but not in men. Each drug may reduce weight by acutely increasing thermogenesis. During four sessions, nicotine (20 micrograms/kg per dosing) or placebo was given to male and female smokers (n = 9 each) via measured-dose nasal spray every 30 min for 2 h after consumption of diet tonic water with or without alcohol (0.5 g/kg). Each nicotine/placebo dosing was followed by assessment of energy expenditure by indirect calorimetry. Alcohol alone induced no significant effect in men or women, whereas nicotine alone and combined with alcohol induced a significant thermogenic effect in men but not women. These results are consistent with other research suggesting a reduced thermogenic responsiveness to drugs in women and indicate that nicotine must act via appetite suppression to reduce body weight in women. Similarly, these findings do not support the notion that alcohol is inversely related to body weight in women because of excessive acute thermogenesis.

Resting energy expenditure in patients with alcoholic chronic pancreatitis

The aim of this study was to assess resting energy expenditure in patients with chronic pancreatitis; 33 patients with alcohol-related chronic pancreatitis (group 1: 13 normal weight, group 2: 20 underweight) and 11 undernourished patients without identifiable disease (group 3) were studied. Body composition was determined by bioelectric impedance analysis and fat-free mass was similar among the three groups (76.4 +/- 1.5%, 78.6 +/- 1.3% and 76.8 +/- 2.1% for groups 1, 2, and 3, respectively). The measured resting energy expenditure (REE) was higher than the predicted EE (Harris and Benedict formula and Cunningham's equation) for the underweight patients with chronic pancreatitis (group 2) (P < 0.05), but not for the two other groups. According to Cunningham's equation, 65% of the group 2 patients were hypermetabolic (REE > 110% of predicted EE) versus 23.1% and 20% in groups 1 and 3. When adjusted for fat free mass, REE was significantly (P < 0.01) higher in group 2 (35.0 +/- 0.9 kcal/kg/24 hr) than in the other two groups (30.1 +/- 0.7 kcal/kg/24 hr and 30.8 +/-1.4 kcal/kg/24 hr in groups 1 and 3, respectively). During chronic pancreatitis, weight loss is accompanied by hypermetabolism, which should be taken into consideration during nutritional support.

Synthesis of fat in response to alterations in diet: insights from new stable isotope methodologies

Synthesis of fatty acids, or de novo lipogenesis (DNL), is an intensively researched metabolic pathway whose functional significance and metabolic role have nevertheless remained uncertain. Methodologic problems that limited previous investigations of DNL in vivo and recent methodologic advances that address these problems are discussed here. In particular, deuterated water incorporation and mass isotopomer distribution analysis techniques are described. Recent experimental results in humans based on these techniques are reviewed, emphasizing dietary and hormonal factors that modulate DNL and quantitative significance of DNL under various conditions, including carbohydrate overfeeding. The somewhat surprising finding that DNL appears not to be a quantitatively major pathway even under conditions of surplus carbohydrate energy intake, at least in normal adults on typical Western diets, is discussed in depth. Nutritional and metabolic implications of these results are also noted, and some speculations on possible functional roles of DNL in normal physiology and disease states are presented in this context. In summary, methodologic advances have added to our understanding of DNL and its regulation, but many questions concerning quantitation and function remain unanswered.

Alcohol and the regulation of energy balance: overnight effects on diet-induced thermogenesis and fuel storage

The effect of alcohol on overnight energy expenditure and substrate disposal was studied in eleven subjects (five men, six women) using whole-body indirect calorimetry for 15.5 h after test meals. Three test meals were studied in random order with at least 48 h between treatments: control, 50% of maintenance energy needs provided as 14, 40 and 46% energy from protein, fat and carbohydrate respectively; alcohol addition, control plus 23% energy as alcohol; alcohol substitution, control with alcohol replacing 23% of carbohydrate energy. ANOVA revealed no significant sex effects. Alcohol-induced thermogenesis dissipated only 15 (SD 14)% of the alcohol energy. Alcohol addition had no significant effect on protein or carbohydrate oxidation but fat oxidation was suppressed (P < 0.0005) to an extent equivalent to storing 74 (SD 51)% of the alcohol energy as fat. Alcohol substitution reduced carbohydrate oxidation (P < 0.009) to an equivalent of 42 (SD 41)% and also spared fat (P < 0.005) to an equivalent of 59 (SD 37)% of the alcohol energy. It is concluded that alcohol has no special thermogenic capacity, and that its energy can be accounted for in a similar way to carbohydrate.

Changes in the fatty acid profile of plasma and adipose tissue in rats after long-term ethanol feeding

The effect of chronic ethanol feeding on the fatty acid composition of plasma and abdominal adipose tissue in rats was studied. Animals were maintained on a 30% ethanol solution in drinking water for 3 and 5 months. Control rats were given water. Caloric intake was similar in control and ethanol-fed rats at the end of the experimental period. However, a decrease in body weight was observed in rats that had consumed ethanol. Palmitoleic (16:1n7) and oleic (18:1n9) acids increased markedly, and linoleic acid (18:2n6) decreased in the plasma and in the adipose tissue of ethanol-fed rats with respect to control rats. After 3 months of ethanol ingestion, long-chain polyunsaturated fatty acids were reduced both in plasma and adipose tissue. When ethanol was administered for 5 months, only plasma long-chain polyunsaturated fatty acids of the n-3 series were decreased. This suggest that changes induced by ethanol ingestion in essential fatty acid metabolism is less pronounced when ethanol feeding is maintained for a long period of time.

Ethanol impairs post-prandial hepatic protein metabolism

The effects of acute ethanol ingestion on whole body and hepatic protein metabolism in humans are not known. To simulate social drinking, we compared the effects of the association of a mixed meal (632 kcal, 17% amino acids, 50% glucose, 33% lipids) with a bottle of either table wine (ethanol content 71 g) or water on the estimates ([1-14C]-leucine infusion) of whole body protein breakdown, oxidation, and synthesis, and on the intravascular fractional secretory rates (FSR) of hepatically (albumin, fibrinogen) and extrahepatically (IgG) synthesized plasma proteins in two randomized groups (ethanol n = 7, water n = 7) of healthy nonalcoholic volunteers. Each study was carried out for 8 h. Protein kinetics were measured in the overnight post-absorptive state, over the first 4 h, and during a meal infusion (via a nasogastric feeding tube at constant rate) combined with the oral ingestion of wine or water, over the last 4 h. When compared with water, wine ingestion during the meal reduced (P < 0.03) by 24% the rate of leucine oxidation, did not modify the estimates of whole body protein breakdown and synthesis, reduced (P < 0.01) by approximately 30% the FSR of albumin and fibrinogen, but did not affect IgG FSR. In conclusion, 70 g of ethanol, an amount usual among social drinkers, impairs hepatic protein metabolism. The habitual consumption of such amounts by reducing the synthesis and/or secretion of hepatic proteins might lead to the progressive development of liver injury and to hypoalbuminemia also in the absence of protein malnutrition.

Chronic alcoholic myopathy and nutritional status

To investigate the prevalence of alcoholic myopathy and its relationship to the nutritional status, we performed a muscle biopsy on the vastum lateralis of 60 consecutive hospitalized alcoholic patients using a Tru-Cut needle, processing it for light microscope and ultrastructural analysis. The nutritional status was assessed by anthropometric measurements such as midarm circumference, triceps skinfold and midarm muscle area, and serum albumin. The hallmark of chronic alcoholic myopathy, fiber muscle atrophy, was present in 33% of the patients, necrosis scarcely being observed (1.5%). Ultrastructural alterations as lipid and glycogen accumulation or mitochondrial and myofibrillar alterations were nonspecific and observed in nearly all the cases where atrophy was present. Malnutrition was frequent in our patients: 39% and 34% showed a triceps skinfold and a midarm muscle area, respectively, under the fifth populational percentile. Patients with muscle fiber atrophy or ultrastructural changes showed a worse nutritional status, not only regarding muscle protein (assessed by midarm muscle area or creatininuria and explained by fiber atrophy), but also regarding fat stores assessed by triceps skinfold. Toxic effect of ethanol and malnutrition may act synergistically leading to chronic alcoholic myopathy.

Alcohol consumption and its effect on the dietary patterns of Hualapai Indian women

Studies of Native American diet have ignored the nutritional and dietary effects of alcohol consumption. Studies of Native American alcohol consumption have largely ignored the socioeconomic characteristics and drinking behaviors of women. Seven-day 24-hour dietary recalls collected from 28 Hualapai Indian women revealed that 12 participants (43%) drank alcoholic beverages. Drinkers frequently skipped meals, yet maintained an energy intake higher than non-drinkers by consuming high calorie alcoholic and non-alcoholic beverages and by eating large restaurant meals. Despite energy intake differences, drinkers and non-drinkers did not differ in body weight or percent body fat. Drinkers were not at risk for protein malnutrition as reported for other female drinkers, but Hualapais' tendency to fast while drinking may increase their risk of liver disease. In contrast to reports of Native American males, female drinkers in this sample were often high school graduates with full-time jobs.

Energy and macronutrient metabolism

In general, obesity is a state of high energy stores, high energy intake, and high energy expenditure. The high energy expenditure is largely due to the increased fat-free mass. The failure to find a positive relationship between reported energy intake and body size reflects a greater under-reporting of calorie intake among obese individuals. Obesity, therefore, develops as a consequence of a chronic imbalance between intake and expenditure, although the cause of this is not apparent from the energy balance equation. However, this equation can be dissected into its component nutrient balance equations because net de novo lipogenesis is negligible in free-living humans. Fat calories are handled very differently from non-fat calories. Non-fat nutrient oxidation rates rise and fall to match the fluctuations in non-fat intake so that non-fat calorie balance is actively maintained. In contrast, changes in fat intake do not acutely affect fat oxidation but are matched by changes in storage. Therefore, within the fat balance equation there is ample scope for a chronic imbalance between fat intake and oxidation. Also, there is some evidence that carbohydrate balance may be an important signal for hunger and satiety. These concepts imply that, under free-living, ad libitum eating conditions, changes in nutrient intake composition (e.g. an increased proportion of fat in the diet) or changes in nutrient oxidation composition (e.g. a decrease in the proportion of fat oxidized) will lead to body weight change (in these cases, to weight gain). Considering obesity as a consequence of normal physiology (with its normal variation between individuals) in a 'pathological' environment (high fat diet, low exercise) offers an important perspective for explaining the interpopulation and interindividual differences in obesity and for formulating treatment and prevention options. Low energy expenditure (relative to body size), high respiratory quotient and insulin sensitivity have been shown to be predictors of weight gain, although upon gaining weight these metabolic factors tend to 'normalize'. Metabolic responses to underfeeding or overfeeding are largely predictable from the changes in calorie intake and changes in body composition, but some adaptive changes may occur.

Alcohol and calories: a matter of balance

Many epidemiological studies show that alcohol-derived calories added to food intake of men and women in amounts of 0-25% of total energy do not appreciably alter the average daily intake of other macronutrients (carbohydrate, fat, and protein). With such lack of evidence for caloric compensation, alcohol and its calories seem to make little contribution to metabolic energy, body weight, or body composition (as indicated by the body mass index, BMI). In fact, a major study by Colditz et al. (Am. J. Clin. Nutr. 54:49-55; 1991) reported a clear inverse relationship between alcohol intake and BMI for women! Research on alcohol metabolism has left unresolved some apparent contradictions regarding the effect of alcohol on caloric control, appetite and satiation, and body mass and composition. To resolve those apparent contradictions, the National Institute on Alcohol Abuse and Alcoholism cosponsored with the National Institute of Diabetes and Digestive and Kidney Diseases and the Beltsville Human Nutrition Research Center of the U.S. Department of Agriculture an all-day workshop titled "Alcohol and Calories: A Matter of Balance" on January 27, 1993. The workshop included sessions on calorimetry and body mass maintenance, alcohol metabolism, thermoregulation, and an overview of energy balance. This report provides summaries of the four discussion sessions at the workshop.

Body weight, fat storage, and alcohol metabolism

Ethanol account for a significant fraction of the energy intake of persons consuming even moderate amounts of alcohol. A recent study has shown that although alcohol does not reveal itself as a layer floating at the top of a drink, metabolically it behaves more like oil than sugar.