Low-carb diet pitted against low-fat PLUS medication (low-carb still wins)

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I suspect there’s always going to be a raging debate about the best way to go about losing weight. From a dietary perspective, a myriad of suggested approaches exist, though within these the two most popular and well-known ‘diets’ are those low in carbohydrate and fat respectively. Both of these approaches have their advocates. I’m generally in the low-carbohydrate camp. Why? Well, one major reason has to do with the fact that when these diets are pitted against each other, the low-carb diets generally outperform low-fat ones in terms of weight loss. Also, low-carb diets generally improve biochemical and physiological markers for cardiovascular disease compared to low fat ones.

I was interested to read a study published yesterday in the Archives of Internal Medicine which, once again, pitted low-carb and low-fat diets against each other [1]. The low-carb diet initially restricted carbohydrate intake to less than 20 grams a day. Calorie intake was not restricted (meaning individuals could eat as much as they liked of permitted foods including meat and fish).The low-fat diet, as is usual in these studies, restricted calories (to produce a deficit of 500-1000 calories a day). In addition, though, individuals eating the low-fat diet took the weight loss drug orlistat (Xenical, Alli) at a dose of 120 mg, three times a day.

Orlistat works by reducing absorption of fat from the gut. A review of the evidence shows that the average weight loss achieved by people taking this drug in studies is about 3 kg (approximately 6.5 lbs).

At the end of the study (48 weeks) the low-carbers had been found to have lost an average of about 11.5 kg in weight, compared to about 9.5 kg loss in the low-fat, medication taking group. This difference was not statistically significant. Unfortunately, this study made no attempt to assess body composition changes. This is a shame, as it’s not really weight loss that is important, but fat loss. However, the subjects did have their waist circumferences assessed, which reflects the extent of ‘abdominal obesity’ (the form of obesity most strongly linked with chronic disease). Here, the low-carbers lost almost an inch more than the low-fat, medication-taking group, though the difference was not statistically significant.

One significant difference between the groups was seen in blood pressure: low-carbers saw an average drop of about 6 and 4.5 points in their systolic (higher) and diastolic (lower) blood pressure. In comparison, the low-fat eaters saw small though non-statistically significant increases in their blood pressure.

Overall, the results of this study show similar weight loss but improved effect on blood pressure for those eating the low-carb diet. On top of this we have the fact that the low-carbers did not need to restrict calories, and did not take medication either. This drug has expense associated with it, as well as potential side effects (including flatulence and ‘oily leakage from rectum’). I’ll stick with the low-carb eating, thanks.


1. Yancy WS, et al. A randomized trial of a low-carbohydrate diet vs orlistat plus a low-fat diet for weight loss. Archives of Internal Medicine. 2010;170(2):136-145

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