Sunday, September 28, 2014

Low Carb Diet Trials: Foster, et al (2010)

 
Participants and Diets
 
307 middle-aged (average age 45.5±9.7) people (99 men, 208 women) with obesity (average BMI 36.1±3.5) were randomised to follow either a low carb diet or a low fat diet.  “All participants received comprehensive behavioral treatment to enhance weight loss associated with both diets”.  The groups were similar at baseline (table 1)
 
Low Carb
Low Fat
Unrestricted fat and protein to eat until satisfied
Limit carbs to 20g/d for first 12 weeks (carbs from low GI vegetables).  Then increase 5g/d per week (more vegetables, small amount of fruit, whole grains and dairy)
Multivitamin
Calorie restriction (1200-1500 women, 1500-1800 men)
15P:30F:55C
Multivitamin
 
Unfortunately, we aren’t told what the groups actually ate, but we are told that the low carb group had more positive results for urinary ketones at 3 months (63% vs. 20%) and 6 months (28% vs. 9%) but not afterwards.  This isn’t surprising given the advice to increase carbs after 12 weeks but may also involve a decline in adherence over time
 
Results
 
Both groups lost ~11% of their initial weight at 6 and 12 months and then regained, achieving a weight loss of ~7% at 24 months.  There were no significant differences in weight loss between the groups at any time point except for greater weight loss in the low carb group at 3 months (table 2).
 
  
The changes in blood lipids were largely what you would expect: the low carb group had a greater increase in HDL-C at all time points and had had greater reductions in triglycerides at 3, 6 and 12 months.  LDL-C decreased in the low fat group whereas LDL-C increased in the low carb group at 3 months, was back to normal at 6 months and was lower at 12 and 24 months.  The lack of difference between the groups in LDL-C and triglycerides at 24 months is probably due to adherence (table 2).
 
Both groups had reductions in systolic and diastolic blood pressure and the low carb group and greater reductions in diastolic blood pressure at 3, 6 and 24 months.  There were no differences between the groups at any time point regarding bone mineral density in the spine and hip, lean mass lost and fat mass lost (table 2).
 
 
 
“A significantly greater percentage of participants who consumed the low-carbohydrate than the low-fat diet reported bad breath, hair loss, constipation, and dry mouth (Table 3). Except for constipation, all of these differences were limited to the first 6 months of treatment”
 
“Attrition included participants who withdrew and intermittent missingness at each time point. In the low-fat group, 6%, 12%, 25%, and 32% of participants did not participate in assessments at 3, 6, 12, and 24 months, respectively. Values for the low-carbohydrate participants were 9%, 16%, 26%, and 42%, respectively (Figure 1)”

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