Sunday, August 31, 2014

Low Carb Diet Trials: Shai, et al (2007)

 
Participants and Diets
 
322 people with CVD or aged 40-65 and with a BMI of ≥ 25 or type 2 diabetes (T2D) were randomised to one of three diet groups: a low fat diet, Mediterranean diet or low carbohydrate diet.  The mean age was 52 years and the mean BMI was 31. Most participants (86%) were men.  The groups were not different at baseline
 
Diet Group
Diet Advice
Low Fat Diet
(LFD)
Calorie restriction (1500 women, 1800 men), 30% fat, 10% SFA, 300mg cholesterol
Mediterranean Diet
(MD)
Calorie restriction (1500 women, 1800 men), high veg, low red meat, ≤35% fat, high MUFA (from 30-45g olive oil and <20g nuts)
Low Carb Diet
(LCD)
20g Carbs for 2 months then gradual increase to 120g, preference for vegetarian sources of protein and fat, avoid trans fat
 
All groups ate fewer calories and the energy change from baseline was not significantly different between the groups.  In all groups (including the low fat group) most of the reduction in calories came from a reduction in carbohydrates
 
Calorie Reduction
Low Fat
Mediterranean
Low Carb
6 Months
458
255
561
12 Months
559
322
591
24 Months
573
372
550
 
Pro:Fat:Carb
Low Fat
Mediterranean
Low Carb
Baseline
18:31:52
18:32:52
19:32:51
6 Months
20:31:50
19:33:50
22:39:41
12 Months
19:31:51
19:33:50
22:39:42
24 Months
19:30:51
19:33:50
22:39:40
 
Results
 
All groups lost weight, where all the weight loss (in all groups) occurred in the first 6 months.  The low carb and Mediterranean groups lost significantly more weight than the low fat group at 24 months.  Women tended to lose more weight on the Mediterranean diet, whereas men tended to lose more weight on the low carb diet
 

All groups had reductions in waist circumference and blood pressure, with no differences between the groups 

 
Low Fat
Mediterranean
Low Carb
Waist circumference (cm)
2.8±4.3
3.5±5.1
3.8±5.2
Systolic blood pressure (mmHg)
4.3±11.8
5.5±14.3
3.9±12.8
diastolic blood pressure (mmHg)
0.9±8.1
2.2±9.5
0.8±8.7

All groups improved their blood lipid profiles, but there were no differences in LDL-C.  The low carb group had a greater increase in HDL-C and reduction in triglycerides and the total:HDL-C ratio relative to the low fat group


Adiponectin significantly increased in all groups, whereas high-sensitivity CRP and alanine aminotransferase (liver enzyme) significantly decreased in the Mediterranean and low carb groups, but not the low fat group.  In these measures there were no significant differences between groups
 
Regarding glucose and insulin levels: 36 participants had T2D and only those in the Mediterranean group had a decrease in fasting glucose, which was significantly different compared to the low carb group.  Insulin decreased significantly in all participants and in all groups, with no difference between groups.  Insulin resistance improved among the T2Ds in the Mediterranean group and was significantly greater than the LFD.  HbA1c significantly decreased in the low carb group but not the low fat or Mediterranean groups.

 
“Among all diet groups, weight loss was greater for those who completed the 24-month study than for those who did not”.  “The overall rate of adherence was 95.4% at 12 months and 84.6% at 24 months; the 24-month adherence rates were 90.4% in the low-fat group, 85.3% in the Mediterranean-diet group, and 78.0% in the low-carbohydrate group (P=0.04 for the comparison among diet groups).”

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