Well, well, well.

• Fat-fighting pill gains approval in US from New Scientist

What have we here?

The drug orlistat – made by GlaxoSmithKline (GSK) and sold as Alli – reduces the amount of fat the body absorbs from food. It is a half-dose version of a prescription medicine called Xenical, sold by Roche.

So basically, this is an artificial reduced-fat diet in your intestines.  You eat a bunch of stuff, orlistat prevents some of it (some of the fat) from being absorbed, and you shit the excess fat out.  Remember how well that worked before?

Most of the (surprisingly negative) press coverage has focused on orlistat’s uncontrollable-liquishits side effects, but let’s step back for a minute and see whether this is a good idea in the first place.

Well, reduced-fat diets are basically reduced-calorie diets: one gram of fat has 9 kcals of energy, some of which gets converted to glucose and (if not used) stored as adipose tissue.  So if you do nothing else but take Alli, you’ll cut some fat from your diet, and therefore some calories.  That’s going to work mildly well in the short term, as reduced-calorie diets tend to do.   The problem there is that your body doesn’t like losing fat — from an evolutionary perspective, fat is your last-resort protection against starving to death.  Therefore, your body would rather slow its metabolism to preserve that life-saving fat (at the expense of, say, muscle) than burn it off and leave you all sexy-lookin’.  (It’s a damn shame, but it’s true.)

Further, if you cut too much energy from your diet, you’ll just convince your metabolism that you are starving to death, and it’ll work as hard as possible to save every last gram of fat.

Now, consider that orlistat only blocks (some) dietary fat… but not all calories are fat calories.  You could eat a pound of sugar or drink a gallon of Coke for lunch, and that lumpy-looking blue pill won’t do squat to keep that sugar from turning into glucose, and then into adipose tissue.  Too many simple carbs in your diet?  This stuff isn’t going to fix your problem.

Okay, so we know that Alli blocks some fat from being absorbed — that means it’ll prevent some fat-soluble vitamins from being absorbed, too.  That’s perhaps not such a good idea.  (Again, orlistat is basically a reduced-fat diet in a pill, so the same goes for other reduced-fat diets.)  I imagine this stuff will also reduce absorption of essential fatty acids and CLA.

Is all of that worth it?  If you look at the weight loss figures reported in the study, you’ll notice that not much is happening.  The control group (low-fat diet plus placebo) lost about five pounds in a year; the experimental group (low-fat diet plus Alli) lost about twelve.  (I’m getting those figures from a CNN report, by the way, not that New Scientist article.)  Honestly, that’s none too impressive.   One can generally expect to lose (or gain) about a pound of body mass a week while staying healthy — if you pay attention and make that work for 90% of the year, that’s about forty-five pounds.  That’s from diligent attention to diet and exercise, incidentally, without the risk of crapping your drawers every time you eat a hamburger.

Further, the study only reports weight loss (you didn’t think I’d leave out my favourite hobby-horse, did you?), not fat loss, changes in body composition, or anything else.  Losing weight is easy — go to the kitchen, grab a steak knife, and saw off an arm.  Presto!  You’ve lost weight.

Is this stuff worth two bucks a day?  I doubt it.