Preventing this weight gain is important because selleck it reduces the health benefits otherwise seen by quitting (Chinn et al., 2005; Davey-Smith et al., 2005; Gerace, Hollis, Ockene, Svendsen, 1991). Avoidance of alcohol is often advocated in smoking cessation support to reduce cues to smoking. People trying to lose weight are often advised to moderate or avoid alcohol because of its relatively high combustible energy value. However, there is contrary evidence on the effect of alcohol on weight gain. Laboratory studies of the metabolic effects of alcohol show three important effects on energy balance. First, alcohol increases energy intake (Buemann, 2002; Tremblay et al.
, 1995; Westerterp-Plantenga & Verwegen, 1999), particularly when consumed in combination with fat (Tremblay & St-Pierre, 1996) and the extra energy from alcohol is not compensated for by reducing subsequent food intake (De Castro & Orozco, 1990; Tremblay et al.,1995; Tremblay & St-Pierre, 1996; Yeomans, 2004). Second, alcohol suppresses fat oxidation, which increases fat storage (Suter, Schutz, & Jequier, 1992). Third, alcohol increases 24-h energy expenditure through inducing thermogenesis by up to 30%. Dietary-induced thermogenesis from alcohol is greater than that from carbohydrate, fat, or protein (Raben, Agerholm-Larsen, Flint, Holst, & Astrup, 2003; Schutz, 2000; Suter, Jequier, & Schutz, 1994; Westerterp, 2004). The first two effects point toward alcohol promoting weight gain and the last effect works against it. So what causes the balance to tip one way or the other? The answer may depend on the pathway by which alcohol is metabolized.
The alcohol dehydrogenase (ADH) pathway produces ATP more efficiently than the microsomal ethanol-oxidizing system (MEOS). It is thought that low levels of alcohol are metabolized by ADH, whereas a high blood concentration of alcohol induces MEOS; and this accounts for the high energy expenditure in people with alcohol dependence (Levine, Harris, Morgan, 2000; Suter, 2005). The threshold level of alcohol for MEOS induction is unknown, but individual variation of body weight, smoking status, gender, and genetic variation in enzymes metabolizing alcohol may explain the different effects of alcohol on body weight (Suter, 2005). Population studies have shown inconsistent results, although this has been explained in part by drinking patterns, smoking status (Cooke, Frost, & Thornell, 1982; Mannisto et al.
, 1996; Tolstrup et al., 2005, 2008), and gender effects (women who drink alcohol seem to gain less weight) (Breslow & Smothers, 2005; Colditz et al., 1991; Gordon, Joseph, & Doyle, 1986; Gordon & Kannel, 1983; Hellerstedt, Jeffery, & Murray, 1990; Wang, Lee, Nanson, Buring, & Sesso, 2010; Wannamethee, Drug_discovery Field, Colditz, & Rimm, 2004; Wannamethee & Shaper, 2003) (Further discussion in Supplementary web appendix 1).