Low-carb diet hype belies the fact there is no cure-all, quick-fix regimen for everyone
Mario Laporta/AFP/Getty Images filesLow-carb dieters who find themselves drawn back to the pizza oven or bread box a few months after following one of the regimens end up feel like "failures" and should seek out other ways to control calorie intake, Jennifer Sygo suggests.
Are low carbohydrate diets finally ready for prime time?
If you take the latest study — published in the Annals of Internal Medicine and widely reported last week — at face value, you might argue that could be the case. In the study, 148 obese men and women without cardiovascular disease or diabetes were randomized to one of two diet groups, and provided with nutrition counselling to support their new dietary habit for a year. One group was asked to follow a diet providing a mere 40 grams of digestible carbohydrates per day (that’s less than the amount in two slices of bread), while the other was counselled on a diet designed to provide less than 30% of their calories from fat.
Not so fast, say some.After a year, the subjects on the low-carb diet lost significantly more weight than those on the so-called low fat diet, and their cholesterol profile also improved more than their fat-minding counterparts. This has led an explosion of media coverage, as well as online discussion and debate as to whether or not we can finally anoint low-carb as “the best” diet for our health.
Yale University professor and researcher Dr. David Katz lambasted the study, calling its core question (low-carb versus low-fat) “dumb,” and implying the journal has lowered itself by even publishing it. Katz’s main issue? At the top of the list is the fact that the low-carb intervention was much more intensive than the low-fat. To wit: while the low carb group was instructed to cut their carb intake by a whopping 75%, the low fat group only needed to drop their fat intake by about 5% (from 35% of their daily intake at baseline, to 30% during the study). And while the low-fat group was advised to eat whole grains and plenty of fibre, the average fibre intake was only 15 grams per day, or about half the target for a healthy adult. The bottom line? The low-fat diet group seemingly did little to change their diets, so it shouldn’t be a surprise that their results looked decidedly mediocre compared to the results for a group who embarked on, and were supported through, a far more substantial dietary change.
While Katz’s points are valid, the study still has some merit: essentially, it demonstrated that, when counselled to stick to existing dietary guidelines, a group of obese adults saw relatively little change in their health and weight. Those people who focused on reducing carbohydrates as their primary target, did see change in their weight. We have seen similar results in other low (loosely defined as eating less than 120 grams of carbohydrates per day), very low (usually 40 grams per day or less), or low-ish (cutting out specific carbohydrate-containing food groups, as in the so-called Paleolitic diet) carbohydrate diets. Subjects on these diets consistently eat less food, and therefore fewer calories. Metabolically-speaking, that’s not much of a surprise when you consider that fat and protein tend to be more satiating than carbohydrates, especially those that are rapidly converted into blood sugar — basically, these diets emphasize foods that are more filling, and reduce those that aren’t.
So why not put everyone on a low-carb diet? There are a variety of reasons, but the biggest issue may be good old-fashioned compliance, i.e., being able to stick with a regimen. In similar studies, almost without exception, the majority of the weight loss and metabolic improvements occur over the first few months, after which subjects slowly drift back toward baseline — and this study was no different.
No single study should, or will, be the final word on nutrition
While they were supposed to consume only 40 grams of carbohydrates per day, the low-carb group never met their target, consuming about 80 grams per day during the first three months, after which their intake drifted to an average of 112 grams per day by the end of the study. Their caloric intake also increased gradually, and their weight loss slowed; in fact, despite the attempted heavy restriction on carbohydrates, the group lost a relatively un-buzzworthy 11.7 lbs by the end of the year (the low-fat group lost an even less-buzzworthy four pounds, but without the drastic dietary change of the low-carb group). And this was after only a year, when the first three months still had a robust effect on the average; it would not be surprising to see the results continue to drift northward the second year and beyond.
So if you have adopted a low-carb diet (or are working towards it), and have seen the light in terms of your own health and weight, then great — I have a number of clients who have follow the diet with great success. But if you know that such a diet spells “disaster” for you — and I’ve had just as many clients who have been “failed” (their words, not mine) low-carbers — then find another path that fits for you. No single study should, or will,
be the final word on nutrition, so treat it for what it is — another piece of the puzzle.
be the final word on nutrition, so treat it for what it is — another piece of the puzzle.
-Jennifer Sygo, MSc., RD, is a registered dietitian and sports nutritionist at Cleveland Clinic Canada, and author of the newly released nutrition book Unmasking Superfoods, (HarperCollins, $19.99). Visit her on the Web at jennifersygo.com and send your comments and nutrition-related questions to her at info@jennifersygo.com.
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