While I was on the cruise, this YouTube video made a splash. It was hailed as the death of the carbohydrate-insulin hypothesis. Take a look:
Several readers emailed to ask what I thought, and I replied that since I hadn’t seen the study itself, I had no opinion yet … although little alarm bells went off in my head when I saw that the researcher being interviewed was Kevin Hall. If the name sounds familiar, perhaps it’s because he was the lead researcher on a recent study that was reported in the media with headlines like FOR FAT LOSS, LOW-FAT DIETS BEAT LOW-CARB DIETS HANDILY, NEW RESEARCH FINDS.
I wrote about that study in this post. The (ahem) low-carb diet provided 140 grams of carbohydrate per day – including 37 grams per day of sugar. Yeah, just like Dr. Atkins recommended. The low-fat diet, meanwhile, was truly a low-fat diet: just 7.7 percent of calories from fat.
Hall responded to that criticism by saying he had to choose a moderate-carb diet to keep protein constant across both diets. Several readers responded to that response by producing (within minutes) two low-calorie diet plans, one very low-fat, one very-low carb, both with identical protein. So Hall’s explanation doesn’t hold up.
The diets lasted a whopping six days each (everyone in the study was supposed to do both diets), and the difference in weight loss was a non-significant one-tenth of one pound.
In the full paper, I saw that 19 people completed the sort-of-low-carb diet, but only 17 completed the low-fat diet … and yet the researchers didn’t restrict their comparison to the 17 people who completed both diets, and didn’t provide individual data for any of the dieters. And the paper included this strange paragraph:
The data were analyzed using a repeated-measures mixed model controlling for sex and order effects and are presented as least-squares mean ± SEM. The p values refer to the diet effects and were not corrected for multiple comparisons. One female subject had changes in DXA % body fat data that were not physiological and were clear outliers, so these data were excluded from the analyses.
My impression was that Hall designed the “low fat beats low carb handily” study to get the results he wanted — perhaps assisted by tossing out a data point or two. Clear outliers, ya know.
Those complaints about his earlier study notwithstanding, if a study is conducted and analyzed honestly, then the data is what the data is. Like I said, I haven’t seen the study he’s explaining in the video. But Dr. Mike Eades took a careful look at the video, screen-capping some of the charts so he could analyze them, and also dug up the abstract. I’d suggest you read his entire post, but here’s the first punchline:
In the video, Hall declares that the study shows there’s no metabolic advantage to a ketogenic diet. Got that? No metabolic advantage. But the title of the abstract is … wait for it … Energy Expenditure Increases Following An Isocaloric Ketogenic Diet in Overweight And Obese Men. And a sentence in the abstract clearly states:
Therefore, an isocaloric ketogenic diet was associated with increased energy expenditure of ~100 kcal/d.
Perhaps it depends on your definition of “advantage,” but that sounds like an advantage to me.
After watching the video and reading Dr. Eades’ post, here’s my opinion of the study: I don’t really care either way. As Paul Jaminet pointed out during a podcast, there are more than a million diet studies in PubMed. You can find almost any result you want. I’ve seen studies in which a lower-carb diet led to more weight loss, even on the same number of calories. This one, for example:
On the 1,800-kcal reduction diet consumed over a 9-week period, diet A contained 104 g carbohydrate/day; diet B, 60 g; diet C, 30 g. The three-man subgroups were matched as closely as possible on the basis of maintenance caloric requirement and percent body weight as fat.
Weight loss, fat loss, and percent weight loss as fat appeared to be inversely related to the level of carbohydrate in the isocaloric, isoprotein diets. No adequate explanation can be given for weight loss differences.
But I’ve also seen studies in which restricting calories led to the same average weight loss whether the diet was low-fat or low-carb. And I suppose if someone did enough digging, he could find a metabolic ward study where people lost more weight on a high-carb diet than a low-carb diet.
Again, I don’t really care. People don’t live in metabolic wards where their food intake is carefully controlled. They live in the real world. And in the real world, people respond to their appetites. For many people, myself included, switching to a low-carb diet resulted in (after years of frustration) losing weight without going hungry.
AHA! THAT MEANS YOU CONSUMED FEWER CALORIES THAN YOU BURNED!
Of course I consumed fewer calories than I burned, you @#$%ing moron! That is always HOW we lose weight. And consuming more calories than we burn is always HOW we gain weight. But as I’ve said many times (and will keep saying until I’m blue in face), HOW we get fat isn’t the same as WHY we get fat.
I tried explaining the difference in this post by pointing out that HOW your toilet overflows (more water entering the bowl than draining out) isn’t the same as WHY your toilet overflows (a clog in the drain pipe). But toilets don’t have appetites, so let’s use (or re-use) a different analogy:
Suppose I have a rather serious alcohol problem that’s affecting my life, and not in a good way. After getting a snootful, I tend to become annoyed by friends and acquaintances who haven’t fully recognized my superior understanding of all things and thus have the gall to disagree with me now and then. So I get in touch to correct their erroneous beliefs and offer strongly-worded advice on how they should fix their lives, careers, diets, social media sites, professional relationships, or whatever – for their own good, of course. As a result, my friendships soon have the life expectancy of a second lieutenant on Iwo Jima.
Waking up with a hangover one afternoon and recognizing the problem may actually be with me instead of everyone else, I vow to limit my drinking to two scotches per day from now on. But no matter how sincere the promise, one drink always leads to another and another and another. Next thing I know, I’m getting punched by strangers in bars for reasons I can’t accurately recall. I curse my lack of discipline and wonder what the @#$% is wrong with me. I really, really, really want to drink less but can’t seem to do it. So I turn to science.
“Why do I drink so @#$%ing much?” I ask the science world.
“Because you’re an alcoholic,” the researchers answer.
“But WHY am I an alcoholic?” I ask.
“Because you drink too much,” the researchers answer.
See the problem? The amount of alcohol I consume only explains HOW I get drunk. It doesn’t explain WHY I get drunk. Because you drink too much isn’t an answer; it’s simply a restatement of the problem.
But now let’s suppose something amazing happens. After making significant changes in my diet, I find my urge to drink has dwindled. I can go out on Saturday night and have two glasses of wine with dinner, then stop. That craving for a third, fourth and tenth drink just isn’t there anymore. (Long-time readers may recognize that this is partly a true story.) It’s not a character issue, because I’m not resisting an urge. The urge is gone.
“Why don’t I get rip-roaring drunk every time I drink like I used to?” I ask the science world.
“Because you don’t drink as much as before,” the researchers answer.
“But I used to have this powerful urge to keep drinking, and now I don’t. So it must have something to do with biochemical changes brought on by the new diet.”
“No, no, no,” the researchers reply. “We’ve done studies on this. If we get 20 people drunk for a week by having them knock back 10 scotches per day, then lock them all in a cell and give them two drinks per day for another week, they’re all equally sober at the end of the second week. Doesn’t matter if they’re alcoholics or not, and it doesn’t matter if we feed them chips or cheese while they’re drinking. So obviously the cause of alcoholism is drinking too much, and the cure is to drink less. It’s simple.”
That two-drink-per-day study may exist, and it may have been honestly conducted and analyzed. But I don’t care. It doesn’t tell me diddly about WHY alcoholics drink too much. It also doesn’t explain WHY a change in diet caused my appetite for alcohol to shrink. Everyone remains equally sober on two drinks per day isn’t useful information for a problem drinker trying to walk past an open bar.
Several studies, including this one, have demonstrated that switching to a low-carb diet causes many people to eat less – even though they’re not counting calories or trying to eat less:
On the low-carbohydrate diet, mean energy intake decreased from 3111 kcal/d to 2164 kcal/d. The mean energy deficit of 1027 kcal/d (median, 737 kcal/d) completely accounted for the weight loss of 1.65 kg in 14 days.
If you spontaneously cut your calories by more than 1,000 per day – and yes, end up consuming fewer calories than you burn as a result – then something very positive has happened to your metabolism. But I don’t think it’s quite as simple and direct as Fewer Carbs => Less Insulin => More Fat Burning. Or to state it in reverse, I don’t think getting fat is as simple as More Carbs => More Insulin => More Fat Storage.
This is already getting to be a long post, so I’ll explain why I believe the “alternative hypothesis” needs some revising in my next post.
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