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

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

  1. Jamie 26 January 2010 at 9:19 pm #


    Just reading through the Medscape report on this study & a couple of things really stand out. Firstly, I’ll say that opponents of low-carb diet interventions will likely fall back to their old-hat criticism of the fact the authors received funding from the RC Atkins Foundation. Putting that to one side however, it makes for interesting reading. Not the least for the number of times the study says no STATISTICAL significance was found between the groups. Now I don’t know about you, but I’m more interested in CLINICAL significance.

    In terms of weight lost, the LC group did lose ~2kg more on average than the LF group. Not a statistical difference, but more weight is more weight. Though like you, I would have liked to have seen what the body composition differences might have been. I think it is important to note that the LC group could eat without calorie limits compared to the LF-orlistat group. Referring back to a previous post that you have made regarding simplicity of eating rules increasing adherence, this does make life a whole lot easier when you don’t have to ensure a certain deficit & remember to take a certain drug. Although in fairness, the drop out rate was 10% higher in the LC group (amounting to approximately 7 people).

    Cholesterol markers improved across both groups, though the Medscape report gave no numbers here. And again, from a clinical significance point of view, these markers may not be that relevant in the grand scheme of things. Also, the authors noted that they included data from those who hadn’t been following their diet particularly well & that this may have watered the results down to an extent.

    What I do think is relevant are the markers for glucose control. Glucose, insulin, & HbA1c improved in the LC group only. Again the report claims that this wasn’t statistically significant. However, I think one would find that any fall in these indicators in an overweight individual will have significant clinical effects in the longer term.

    Blood pressure fell more significantly in the LC group, with the authors hinting at a role for insulin here. I suspect that both insulin & decreases sodium intake may account for this, as when you knock out many carbohydrate forms such as bread, cereals, and other processed foods, you concurrently reduce the glycaemic load & a significant number of vehicles for added salt in the diet.

    The authors comment that one diet is not superior to the other. I however beg to differ on the basis of this statement in the Medscape report:

    “In another important finding, Yancy et al point out that while a small number of study participants initiated hypertension or diabetes medications over the course of the study in both diet groups, a much higher number actually decreased or discontinued their dosages, with a higher proportion of patients discontinuing or lowering their dosages in the low-carb group.”

    So amongst all the other clinical differences, those in the LC group were also more likely to decrease or discontinue medication. This is very significant when one remembers that each drug will have their own side effect profile plus likely have a further interaction profile with other meds. Sure a drug might be great for lowering someone’s insulin levels but not at the expense of trashing their liver & kidney’s in the long haul. There is also the extended benefits in terms of the reduced public healthcare cost when less publically funded drugs are being consumed.

    So on the basis of the bigger CLINICAL picture other than just weight lost, I suspect the LC diet has the overall edge. That said, I also believe in horses for courses & I think studies like this are important in emphasising that there isn’t a one size fits all approach as conventional wisdom would have us believe. I would hope that this study causes those who routinely dismiss LC diets as an option to take some pause for thought.

  2. Antje 29 January 2010 at 4:00 pm #

    Doctor Briffa,

    could you please help me to to find an answer to the question:

    what exactly is considered te be a low carb diet? How many grams of carbs a day? Which percentage of one’s caloric intake?

    Thank you!

  3. Dr John Briffa 29 January 2010 at 4:18 pm #


    There is no widely recognised definition regarding what a low-carb diet is, though I think there would be general acceptance of the view that it is a diet which offers 50-150 g of carb a day.

  4. Antje 29 January 2010 at 6:57 pm #

    Thanks for your reaction. The cabs issue is a big one for me. I have studied it and tried to reduce my intake.

    i have another question; can you recommend a book on how exactly to reduce your carb intake? Which tempo etcetera?And how much more protein one should eat? Since i live in Holland i do not suppose you can recommend a doctor.

    i am a sportswoman. Reducing my carbs intake to 120g made me confused to a point where i lost my- normally perfect – memory . Friends took me to the hospital. All tests came out excellent. Eating half a jar of raw honey brought me back.

    Thanks again, Dr Briffa, for your very interesting stories. Please keep on with this work.

  5. Dr John Briffa 29 January 2010 at 7:07 pm #


    Perhaps try this:


  6. Mary Lomax 29 January 2010 at 10:55 pm #

    Hi Dr Briffa
    I wonder what your views are on the effect of biochemical individuality on our abilities to utilise different fuel sources effectively and how this affects our requirements for carbs and fat. One source of info can be found here http://www.bloodph.com/about-typing.html. It makes sense to me that there is a variation in what we are suited to eat and that this explains why research always deals in percentages of improvement. And also why there are many books and practitioners touting different systems most of which have genuinely benefited from a particular way of eating and wish to share this with others.
    And perhaps this is also one of the reasons why some people find it hard to adhere to a certain regime and drop out of the study (along with many other reasons of course)

  7. Margaret Wilde 30 January 2010 at 11:49 pm #

    The fast, safe way to reduce excess weight is to cut down on salt and salty food. This has a host of other health benefits too.

    If you are overweight and wanting to lose weight why not try it? You have nothing to lose but your excess pounds/kilos…(o: – And you will feel soooo much better.

  8. Hilda Glickman 31 January 2010 at 9:04 pm #

    Cutting out salt will just help you lose water, not fat and can be dangerous if you go too low.

  9. Sue 9 February 2010 at 11:54 pm #

    What difference do you think it makes that one group were receiving medication and the other wasn’t? Surely an odd methodology?

  10. Dina 21 April 2011 at 11:35 am #

    I have always found the low-carb approach very effective, but since I started on hypertension drugs (atenolol and lisiprinil) I have been unable to lose any weight despite scrupulous adherence to the regime. What is happening here, and what can I do?

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