Dr. Michael Greger on the science of weight loss that lasts (#29)

The 3500 calorie rule is wrong. What's right?

How many calories do you have to cut to lose one pound, sustainably? And how long would it take?

The rule used to be 3500 calories. So if you cut 500 calories per day for one week (500 x 7 = 3500), you would lose one pound per week.

But, this fails to take into account how your body changes when you start losing weight. ¹ “The most serious error of the 3500-kcal rule,” wrote researcher Dr. Kevin Hall, “is its failure to account for dynamic changes in energy balance that occur during an intervention.”

So, what’s the real answer?

Enter Dr. Michael Greger and his book, How Not To Diet: The Groundbreaking Science of Healthy, Permanent Weight Loss .²

Picking up on our January health and diet theme, Dr. Greger shows us what the research now points to as the new rule for cutting calories, and how long it takes to sustain it.

Let’s get it.

To show why the 3500-Calorie Rule is wrong, Dr. Greger paints an exaggerated, but helpful picture:

Imagine a thirty-year-old sedentary woman of average height who weighs 150 pounds. According to the 3,500-calorie rule, by cutting 500 calories from her daily diet, she’d lose a pound a week or 52 pounds a year. In three years, then, she would apparently vanish. She’d go from 150 pounds to -6. Obviously, that doesn’t happen. What would happen is that, in the first year, instead of losing 52 pounds, she’d likely only lose 32 pounds and then, after a total of three years, stabilize at about 100 pounds.

So in this case, even in the first year, the 3500-Calorie Rule overestimates by almost double.

Why does this happen? There are at least four reasons, with the first one being simple: “it takes fewer calories to exist as a thin person.”

Part of it is simple physics in the same way a Hummer requires more fuel than a compact car. Think how much more effort it would take just to get out of a chair, walk across the room, or climb a few stairs while carrying a fifty-pound backpack.

Second, as you lose weight, your body starts to conserve.

Because of our millions of years of evolution hardwiring us to survive scarcity, when we start losing weight, we may unconsciously start moving less as a behavioral adaptation to conserve energy.

Third, your metabolism adapts.

There are metabolic adaptations as well. Our metabolisms slow down. Every pound of weight loss may reduce our resting metabolic rates by seven calories a day. This may only translate to a difference of a few percentage points for most, but it can rapidly snowball for those who achieve massive weight loss.

Fourth, your appetite “revs up.” Your body will also, unconsciously, tell you to start eating more. (Though this can be combated by simply tracking what you eat so, even if you are hungrier, the eating isn’t “unconscious”).

Bottom line: there’s a lot fighting in the other direction.

The Solution: Ten-Calorie Rule + Timeline

First, Dr. Greger offers some simple online tools that “take into account the dynamic changes that occur when you cut calories.”³ .

But, if you’re not a nerd (me) and you don’t want to fool around with online calculators, he advises you follow the “Ten Calorie Rule.”

Every permanent, ten-calorie drop in daily intake will eventually lead to about one pound of weight loss.

The key word is “eventually.” You have to pay attention to the time period. It takes a little longer than most people think for your body to “accept” the new weight:

It takes about a year to achieve half the total weight change and about three years to completely settle into the new weight.

So cutting five hundred calories a day can cause the fifty-pound weight loss predicted by the 3,500-calorie rule, but that’s the total weight loss at which you plateau, not an annual drop, and it takes about three years to get there. A five-hundred-calorie deficit would be expected to cause about a twenty-five-pound weight loss the first year and then an additional twenty-five pounds over years two and three, but that’s only if you can maintain the five-hundred-calorie deficit.

The OGT

There are three critical takeaways. They are useful conceptually, even if the numbers aren’t exact.

First, when you begin losing weight, your body has built-in, survival mechanisms that try to stop you from losing more weight. Second, we probably have been overestimating how much weight can be lost per calorie cut.

Last—and most critical— if you’re trying to lose weight sustainably (i.e., beyond just your wedding shoot), push out your time horizon. As Robert Greene advises, “make time your ally.”

If you cut 200 calories per day, and stick to it (you should track your eating to be sure), you will achieve your 20 pound weight loss goal. But—the first year will only be half of that weight loss. For the full 20, allow another 1-2 years.

You’ve got time.

For more on weight loss and habit change, revisit how Penn Jillette lost 100 pounds (and kept it off), Haruki Murakami on how to quit smoking, and Professor Kelly McGonigal on the secret to more willpower.

1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2376744/

2. Dr. Greger is a decidedly plant-based skewed doctor. In his book, it’s not surprising that many of his findings point to eating more plants, and eating less animal. When potential bias exists, I like to focus on Thinks that don’t relate to the bias. In this case, the science behind calorie-cutting.

3. The Body Weight Planner from the National Institutes of Health (NIH) and the Pennington Biomedical Research Center’s Weight Loss Predictor out of Louisiana State University (LSU).

*Dr. Greger says that NIH planner is more accurate.