Dr. Joan Bushwell's Chimpanzee Refuge

Ever efficient, the citizens of Great Britain are reportedly killing two health birds with one stone by tacking on an extra day’s worth of calories each week in the form of alcohol. I doubt they’re alone in the industrialized world in this regard. (The linked article mentions something called “alcopop,” which sounds like either the sound made by cracking open a beer or something your dad becomes after a few too many, but is evidently a beverage.)
Many people know the basics about the energy supplied by the three main macronutrients: Carbohydrates and proteins each supply 4 calories (actually kcal, but obviously no one’s really counting) per gram, while fats provide 9. Ethanol, while technically a carbohydrate, has a yield of about 7 calories per gram. That means that a one-ounce (28-gram) shot of 40-percent-by-volume (80-proof) vodka or other spirit offers about 70 calories. (Seven times [0.4 * 28] = about 80, but this simplified calculation ignores the different densities of water — 1 g/ml — and ethanol — 0.79 g/ml).

We’ve all heard of (or grown) “beer bellies,” but many have probably noticed that those unfortunates who have crossed the sometimes-fuzzy line into frank alcoholism are typically underweight, and in many cases experience a marked weight loss — this despite taking in, say, a half-gallon of vodka per day for extended periods.
While this intake in theory totals close to a whopping 5,000 calories a day for people who are probably not doing a whole lot of aerobic exercise outside of Brownian staggering, the way in which ethanol is metabolized (at least before the liver goes ass-up) creates something of a thermogenic effect. Very little alcohol is converted to fat — perhaps only about 5 percent; the reason most drinkers gain weight is that alcohol, in the form of acetate, effectively replaces circulating fats as a source of immediate fuel, driving any fats ingested that much more quickly toward bellies, asses and hips. (This site explains this phenomenon and also notes that, to add to the fun, a single binge can lower testosterone levels. Bottoms down, amorous fitness buffs.)
As a result, people who merely drink “too much” but continue eating will usually gain weight, but those who are literally living on booze have no ingested fats to shunt toward adipose tissue. I don’t know if I’d go so far as to call this a silver lining, but there it is anyway.