Saturday, October 18, 2014

Low Carb Diet Trials: Bazzano, et al (2014)

 
Participants and Diets
 
148 people (mean age, 46.8 years; 88% female; 51% black) with a BMI of 30-45 and without CVD and T2D were randomised to a low carb diet or a low fat diet.  The groups were similar at baseline (Table 1)
 
Low Carb
Low Fat
<40g Carbs (excluding fibre)
Fibre 25g, prefer MUFA, limit/eliminate TFA
<30% Fat, <7% SFA, 55% carb
Fibre 25g, prefer MUFA, limit/eliminate TFA
 
“We also provided 1 low-carbohydrate or low-fat meal replacement (bar or shake) per day to participants in each group for the duration of the study”
 
“Participants met with a dietitian in weekly individual counseling sessions for the first 4 weeks, followed by small group counseling sessions every other week for the next 5 months (a total of 10 sessions) and monthly for the last 6 months of the intervention.”
 
 
Low Carb
Low Fat
Pro:Fat:Carb
Δ Calories
Pro:Fat:Carb
Δ Calories
Baseline
17:33:48
0
18:35:46
0
3 Months
26:43:29
-740
19:28:53
-616
6 Months
26:43:28
-674
18:28:52
-553
12 Months
24:41:34
-550
19:30:54
-507
 
Physical activity levels were similar throughout the study.  For more detailed info on nutrient intakes see table 2 below
 

Results
 
Both groups maintained significant weight loss at 12 months and the low carb group lost significantly more weight at all time points.  The weight loss in the low carb group came largely from fat loss as the % of lean body mass increased.  Whereas in the low fat group the % of lean and fat mass didn’t change.
 
 
 
At 12 months the low carb group had greater improvements in HDL-C, triglycerides, the TC:HDL-C ratio and the Framingham Risk Score.  In addition
 
  • There was no significant change in TC or LDL-C
  • Systolic blood pressure was significantly lower in both groups at 3 and 6 months, but was not maintained at 12 months
  • Diastolic blood pressure was significantly lower in the low carb group at 3 and 6 months
  • CRP slightly increased in the low fat group (NS) and slightly decreased in the low carb group (NS).  The difference between the groups was significant
  • Creatinine was significantly decreased in both groups at 12 months, perhaps indicating improved kidney function
 
 
75% completed the trial in the low carb group and 73% completed in the low fat group.  There were no differences between the groups regarding ‘symptoms’ except more participants in the low fat group reported headaches at 3 months

4 comments:

  1. R.D. Feinman's comment on this study for Medpage Today is priceless.
    http://www.medpagetoday.com/Endocrinology/GeneralEndocrinology/48125

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    Replies
    1. That was a good article. I'm guilty of not properly acknowledging the short term studies too.

      Although I think there's an argument on both sides. A short term/high intensity intervention is better for assessing the diet, while a long term/low intensity intervention is better for assessing the effect of dietary recommendations (feasibility, sustainability, etc). You need both

      I agree with the reporting bias. There's a 'guilty until proven innocent' view that many people have when discussing low carb diets

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  2. Only a trial with 100% compliance tells you what it is that you are actually advising.
    You would test the pure version of a drug, not allow it to be diluted or avoided.
    Once you know the "pure" value of an intervention, only then check the "street" value.
    If doctors and patients know that an advised intervention, when complied with fully, has proved highly effective, compliance will tend to increase,
    We've been doing things backwards by using intent-to-treat analysis first and only.
    R.D. Feinman has been saying this for years.
    The advice has X value at Y point in time - but why don't we find out the true and absolute value of the thing we are advising first?

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