Blasting the "no carbs after 6pm myth" myth

A dude over at the Team Beachbody message boards (part of my day job) pointed out a study today indicating that loading carbs in the evening can actually induce weight loss. A host of bloggers have picked up on said study and are touting it as the death of the "no carbs after 6 pm myth." The death? Really? That's a bit grandiose, isn't it? Let's break it down.

First, the study from the journal Obesity. Here's a nice little summary from Hive Health Media:

In total, 78 police officers with BMI’s over 30 were randomly assigned to two identical low-calorie diets. In the experimental group, they consumed carbohydrates mostly at dinner while in the control group, they consumed carbohydrates throughout the day. Both groups followed their respective diets for a duration of six months.

Again, both groups followed the same standard low-calorie diet consisting of (20% protein, 30–35% fat, 45–50% carbohydrates, 1,300–1,500 kcal) per day with the only difference being the timing of their carbohydrate intake.

This isn't surprising at all. I don't think the cops lost weight because they ate carbs with dinner. They lost weight because they didn't eat carbs during the day. They were all obese (I'm going to assume the 30 BMI wasn't caused by muscle weight), so the lack of blood sugar would have triggered mobilization of body fat stores. But to test this diet properly, there really needs to be a third group eating a high-protein diet to measure the results against - which there was not.

A fourth group that wasn't overweight would have been nice too.

Also, the fact that they were eating at an extreme deficit makes a huge difference. Odds are, the lion's share of those dinner carbs went to replacing glycogen stores and blood sugar that were tapped out during the day. Furthermore, 45-50% of a 1500 calorie diet is massively different from 45-50% of a 2400 calorie diet. In fact, it's an over 100 grams difference if we're referring to carbs. Someone eating an average, healthy diet who loads all his or her carbs into dinner is looking at 300 grams in a sitting!

And by the way, the notion that nutrition experts all say "No carbs after 6pm" is rather dated. No one says that anymore - at least not the cool nutrition experts. What they advise is to avoid porking out in general in the evening. If you take in a bunch of calories and then then just sit around or sleep - as usually happens at night - all that energy has to go somewhere. Furthermore, if you eat those calories too close to bedtime, there are studies showing that digestion interrupts sleep cycles, which leads to a poor night's sleep. An obese person eating a mostly carb dinner as part of a 1500 calorie diet is going to digest those those carbs super-fast. The abstract of the study doesn't mention exact meal times, but if it's around 6 or 7pm, it's safe to assume that they had plenty of time to digest.

In summary, if you're obese and you're eating at a severe deficit, then, yeah, go ahead and save your rice allotment for the evening. Otherwise, there needs to be A LOT more research before this study has any bearing on the rest of us.

Here's where to get that hat.