Low carb diet improves glycemic control compared with advice to follow a low-fat diet
This is an interesting study as it looks at real world situations with "few resources allocated for achieving compliance, so that clinical use of the protocol would be realistic for many providers of care." The specific terminology used in this study shows that we are looking at what the effect of the advice does to the outcomes measures. Bear in mind that this therefore means that individuals on the low fat diet may have not been eating 'low fat', or those on the low carb diet may have not been eating 'low carb' but compliance in the study did seem to be good based on a zero dropout rate and food diary records. Another thing to mention here is that in the 'low carb' diet it was replaced by both fat AND protein so the beneficial effects in this study are linked to a low carbohydrate diet not necessarily a high fat or high protein diet. This is somewhat of a moot point as consuming more protein often leads to a concomitant increase in fat and vice versa… e.g. eggs, steak, bacon, nuts, dairy etc.
(A quick note, for those of you who may have missed the previous study on Low carbohydrate High Protein diets that we posted, you can get information and websites by clicking this LINK.)
As we jump quickly to the conclusion as it rings true with a question that was posted on our old Q&A page about the ability of dietitians to 'not toe the exact party line' of the Government/NICE guidelines. Dietitians can, and do, use these methods on a regular basis; the only real requirement is that their practice is evidence based. Obviously this means those who want to act outside of the 'EatWell' (haha) Plate need to be on the top of their game with knowledge of current literature and may even be asked to provide 'proof' which again doesn't make for an easy working life but who ever said greatness was easy?
Anyway, here we are making dietitians lives a little easier. Evidence! Specifically, here is what the very balanced conclusion of the study stated:
Thus, aiming for 20% of energy intake from carbohydrates is safe with respect to cardiovascular risk compared with the traditional LFD and this approach could constitute a treatment alternative.
See what we mean about balanced? Nothing extremist there! We need to look at the results to actually find out why it could constitute a treatment alternative. First though, some basic info on the methods.
- Kcals were controlled at 1600 and 1800kcals per day for women and men, respectively.
- Low Carbohydrate Diet (LCD) consisted of 50% fat, 20% carbohydrate and 30% protein.
- Low Fat Diet (LFD) was similar to the traditional diet recommended for the treatment of type 2 diabetes: 30% from fat (not low in my opinion) of which less than 10% from saturated fat, 55–60% carbohydrate and 10–15% protein
- Follow up meetings were only held for 12 months. The second year the subjects were still studied but not supported.
- In contrast to many other studies, the LCD was not told to avoid sources of saturated fat.
- Intention to treat analysis was used so even though 4 people in the low carb group and 3 people in the low fat group said they would have "severe difficulty following the prescribed diets and were not willing to participate in the group meetings." they were still used in the analysis of the results. Bear that in mind.
- Similarly, at 2 years, 4 individuals in the LFD group and 10 in the LCD group did not provide diet records… Presumably because they were not following the guidelines that had been put in place for them but, their outcome measures were still used in the analysis.
For those of you who are confused by those last two bullet points, basically, because the study is looking at the effect that the advice has on people's health, it's not necessarily looking at what effect the specific diet had on their health. So if a group of people are advised to do one thing but they ALL do something else, it's pointless to give them that advice in the real world setting. This also gives us some good ideas about why differences might be seen early on when people are complying but then there are no differences later on when people's motivation or dedication is waning.
Low Carb vs Low Fat RESULTS!
- There was no difference in weight reduction between the groups at 6 months
- A significant reduction in HbA1c, a key diagnostic tool of diabetes, was seen at 6 months in the low-carbohydrate group only but this was not seen at 24 months.
- The reduction in insulin medication was statistically significant only in the low-carbohydrate group at 6 months
- At 6 months, the low-carbohydrate group showed significantly increased levels of HDL-cholesterol
- The percentage of energy intake from saturated fat increased in the low-carbohydrate group throughout the whole study
- The high-fat group had lower compliance at 24 months based on 'completers' vs whole cohort data
In those who did appear to comply all the way up to 24 months
- Subjects on the LCD lost 2cm off their waist whilst those on the LFD did not have any reductions
- Subjects on the LFD reduced blood pressure whilst those on the LCD did not
- HDL-cholesterol (the so called good one) increased to a significantly greater extent in LCD compared to LFD although HDL did increase from baseline in the LFD
Note that all of the above was with differences in weight loss between groups. In fact, in absolute terms, the LCD group lost around 30% less weight yet had significantly better improvements in the measures outlined above. All in all this study shows that with VERY few resources, advice to follow a low carb diet is at worst not detrimental and realistically has some positive outcomes especially in the short term. The discussion of this study highlights that results in weight loss were conflicting to many other studies, which find lower carb diets to be better but state that with only 4 meetings in 12 months it was hard to guarantee compliance. Other studies that have shown LCD led to greater weight loss used as many as 18 group meetings to keep individuals on the 'straight and narrow'.