Sunday, September 14, 2014

Low Carb Diet Trials: Brinkworth, et al (2009)

 
Participants and Diets
 
118 people aged 18-65 with obesity and ≥ 1 other metabolic syndrome risk factor were randomly assigned to either a low carb diet or a low fat diet.  The diets included calorie restriction (~1430 for women and 1670 for men) and were matched by calories (isocaloric).  This was done to measure the weight and metabolic effects of LC and LF diets without confounding variables such as differences in calorie intake.  The groups were similar at baseline.
 
Diet Group
Target Pro:Fat:Carb
Other
Low Carb
35:61:4
Carb <20g for week 1-8, <40g thereafter
Low Fat
24:30:46
SFA <10g and <8%, additional 20g carbs for week 9-52 to remain isocaloric
 
Both groups adhered very well to the calorie and macronutrient targets owing most likely to the high level of support in the trial and of self-monitoring (see methods)
 
 
Low Carb
Low Fat
Pro:Fat:Carb
Calorie Intake
Pro:Fat:Carb
Calorie Intake
Weeks 1-8
35:57:5
1572
23:27:45
1509
Weeks 9-24
33:56:8
1605
23:27:45
1520
Weeks 25-36
33:55:8
1620
22:27:45
1555
Weeks 37-52
32:55:9
1644
22:26:46
1624
Target
35:61:4
1430-1670
24:30:46
1430-1670
* Unfortunately we aren’t given baseline calorie intake
 
Although the low carb adhered to the macronutrient and calorie targets very well, the diet wasn’t very ketogenic, perhaps due to the protein intake, which wasn’t that high at ~130g, but might have been high enough
 

Results
 
Both groups lost a significant amount of weight, but there wasn’t a significant difference between the groups (p =0.22 for total, p = 0.14 for the completers)
 
 
 
Both groups had significant (and often quite impressive) improvements in blood pressure, fasting glucose, insulin, insulin sensitivity and CRP, with no difference between the groups (see table 3)
 
Total cholesterol, HDL-C and LDL-C increased, while triglycerides decreased in the low carb group relative to the low fat group (see table 4).  There was no significant difference in the change between groups in non-HDL-C (p = 0.09) and Apo B (p = 0.17) between the groups*
 
60.0% in the low carb group completed the trial, whereas 69.2% in the low fat group completed the trial.  Given the low carb diet included calorie restriction and more restrictive macronutrient targets I’m surprised at the relative lack of difference
 
This trial is quite unique regarding how well the participants adhered to the diets.  The weight loss and improvement in metabolic markers was far greater in this trial than others, probably due to the extra support improving adherence.  It’s interesting that the participants in this trial reported calorie intakes similar to those in other trials, but experienced roughly 3x more weight loss, perhaps suggesting that the participants in the other trials were underreporting their calorie intake (at least to a greater degree than the participants in this trial).  Although we don’t know the baseline calorie intake among the participants in this trial so we can’t be sure.

Sunday, September 7, 2014

Low Carb Diet Trials: Davis, et al (2009)

 
Participants and Diets
 
105 People aged > 18, with T2D for at least 6 months, BMI ≥ 25 and A1c 6-11% were randomly allocated to a low carb group or a low fat group.  In this trial, 82 of the participants were female and 67 were classified as black.  The groups were similar at baseline
 
Diet Group
Diet Advice
Low Carb
2 Week phase of 20-25g carbs, 5g carb increments each week
Low Fat
Fat gram goal (25% of total calories)
 
“At randomization, all participants received 45 min of individual dietary instruction by a registered dietitian and were given a specific gram allowance of carbohydrates or fat to achieve a 1-pound weight loss each week. Structured menus that provided meal choices and recipes were used for the first 2 weeks. After the first 2 weeks, participants were instructed on selecting foods that met their dietary goals without using the menus. During the 12-month study, participants had a total of six scheduled, 30-min visits with the dietitian for additional dietary counseling.”
 
“We provided participants with general recommendations to achieve 150 min of physical activity each week, but physical activity was not an emphasis of the study.”
 
Pro:Fat:Carb
Low Carb
Low Fat
Baseline
20:36:44
19:39:41
6 Months
23:43:34
21:31:48
12 Months
23:44:33
19:31:50
 
Reduction in Calories
Low Carb
Low Fat
6 Months
-331
-341
12 Months
-210
-53
 
Results
 
The LC group lost more weight and had better improvements in metabolic markers at 3 months (not sure if significant), but regained some of the weight loss and didn’t maintain those improvements at 12 months (see table 2)
 
 
 
3 months
6 months
12 months
HbA1c (%)
Low Carb
−0.64
−0.29
−0.02
Low Fat
−0.26
−0.15
0.24
Systolic blood pressure (mmHg)
Low Carb
−5.80
−0.78
2.00
Low Fat
−0.98
−3.70
−1.80
Diasystolic blood pressure (mmHg)
Low Carb
−2.20
−0.93
−2.90
Low Fat
−0.40
0.95
−2.20
 
Overall, there were no significant improvements in systolic blood pressure, diastolic blood pressure HbA1c and blood lipids in either group, except that the low carb group had a significant increase in HDL-C at both 6 and 12 months (see table 2)
 
There was no difference in the number of participants who completed the trial (44/50 (88%) in low fat group, 47/55 (85%) in low carb group).

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).”