Dear Science,
My friend's trainer at the gym told her she didn't need to buy any of the fancy supplements they were selling there. He said she should just take an aspirin and drink a glass of grapefruit juice every morning, and it would speed up her metabolism. Is the grapefruit juice/aspirin thing true? Do the supplements they sell at the gym do anything real? Thanks!
Burning Belly
Dietary supplements are a pit of despair for science, a den of bold unproven claims held to irrational depths by legions of believers. Before overturning that rock, let's talk about metabolism.
Like cars, we consume energy as we go about our business—measured in kilocalories; for surreal reasons, food packages just call them calories. One kilocalorie is the energy needed to heat a liter of water one degree centigrade. A typical person requires somewhere between 1,500 to 3,500 kilocalories worth of energy per day just to exist—called the basal metabolism. This is what your friend wants to increase, to speed up—becoming less efficient, more Hummer than Prius.
Tremendous variation exists from individual to individual in this rate; you can experimentally determine yours. Over the course of a couple weeks, weigh yourself each day and then calculate your seven-day rolling average weight to see if your weight changed over time. Record what and how much you eat over this time, using food calorie tables to determine the total calories you ate during the test period. A program like CRON-o-Meter is perfect for this. Each pound of fat contains about 3,500 kilocalories, so for each pound you gained or lost, subtract or add 3,500 kilocalories respectively from the total. Then calculate the average number of calories you ate per day. This is your basal metabolism. Science, doing this, found his basal metabolism is about a thousand kilocalories less a day than the average person's of his gender, height, weight, and activity level; he fears cookies.
An astounding number of drugs can increase or decrease the basal metabolism. For example, ephedrine—known to most people around here as pre-meth—increases basal metabolism and suppresses appetite. Thanks to hideous side effects, this is a poor long-term dieting strategy.
What about those gym supplements? Like all supplements, there is no legal requirement for testing if they are safe, if they work, or even what is in the supplement; for all we know, many supplements are shredded Chinese newspapers.
What of the trainer's combination? Aspirin increases the effect of drugs like ephedrine. Grapefruit juice can slow down the destruction and removal of a wide variety of drugs, increasing the effect of metabolism-modifying medications. Like the supplements, who knows if they'll increase your basal metabolism. Science suggests you do some self-experimentation and report back.
Inquisitively Yours,
Science
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