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To review the available information on the mechanism of ketogenesis, the effect of diets of differing degrees of caloric restriction, the advisability of caloric restriction in GDM based on present knowledge, and directions for future research.

Article inclusion methods not described.  Feeding studies included subjects who were:

• Obese (>120% DBW)
• 30 to 31 wk gestation

None specifically mentioned.

Recruitment:  12 women with gestational diabetes were followed for a 2 wk period in clinical research center of University of Washington Hospital.

Design:  Review of 2 feeding studies.

Blinding Used (if applicable):  not applicable

Intervention (if applicable):  Study 1 compared the affect of kcal restriction on glycemic control and Study 2 compared calorie restriction with insulin therapy on glycemic control.

Statistical Analysis:  not performed in review

 

 

Timing of Measurements

Data collected on days 6, 7, 13 and 14 of Study 1.

Dependent Variables:

• Fasting glucose
• 24-hr mean glucose
• Plasma immunoreactive insulin
• Free fatty acids
• Plasma b-hydroxybutyrate
• Urine ketones
• Plasma trigylcerides

Independent Variables

• Study 1 compared the affect of kcal restriction on glycemic control: Week 1:  Diet: 2400 kcal, 50% carbohydrate, 30% fat, 20% protein, 11 g fiber. Distribution of kcal: 25% at each meal and 12.5% each for snacks at 3 p.m. and 10 p.m.  Week 2:  Women were randomized to 2400 kcal or 1200 kcal diet..
• Study 2 compared calorie restriction with insulin therapy on glycemic control:  Week 1:  2400 kcal, Week 2:  1655 kcal (33%)

Control Variables

Initial N:  2 feeding studies, 12 women in both studies.  63 references included.

Attrition (Final N):  see above

Age:  see Results

Ethnicity:  not described

Other relevant demographics:

Anthropometrics:

Location:  University of Washington Hospital

Study 1:

5 women continued the 2400 kcal diet on week 2;

(mean age 36 yr, weight 88 kg)

7 women consumed a 1200 kcal diet on week 2.

(mean age 30 yr, weight 96 kg)

Effects of 50% calorie restriction on plasma fuels and insulin on obese women with gestational diabetes:

Kcalories

	2400	1200	% D
Glucose (mM)
Fasting	5.9	4.9	-17
24-hr mean	6.8	5.4	-21
(P<0.001) for mean glucose
Insulin (pM)	265	146	-45
FFA (mg/L)	220	360	+ 64
b-OHB (mM)	290	780	+269
Urine ketones (+)	1.0	2.1	+110
TG (mM)	3.1	2.9	-7

Study 2:

9 normal weight women (24.1+4.9 yr)

7 obese                            (25.7+3.5 yr)                    

6 obese GDM.                 (28.8+5.6 yr)

(3 controlled with diet, 3 with insulin)

Significant differences in weight

Obese( 128+6%) and obese GDM (132+15%) (P<0.0005)

Comparison of insulin vs diet

	Controls	Diet	Insulin
	(n=9)	(n=3)	(n=3)
Glucose (mM)
Fasting	3.9	3.7	4.2
Insulin, (pM)	127	138	255
Urine ketones (+)	0.7	1.7	1.5
FFA, mg/L	100	83	157

These observations indicate that a substantial improvement in glycemic status can be achieved with a caloric restriction of as much as 50%. However, this improvement in glycemia was achieved at the expense of a 60% increase in plasma FFA concentrations and a 2.5-fold increase in plasma b-hydroxybutyrate concentrations. 

Because the impact of this amount of caloric restriction maintained over a long period of time on fetal growth and development is unknown, a specific dietary recommendation based on these data can not be made.

In study 2, comparing diet vs insulin treatment in GDM, fasting plasma glucose and TG reductions were both greater in the diet-treated group compared to the insulin treated group.  Only 1 of the subjects in the diet treated group experienced ketonuria on the 1600 kcal diet.

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This article is a review of several studies done by the authors and some detail is left out of the study.

Small sample size.

Some of the changes must have been significantly different with reduction in kcal, but not documented in this paper.

In study 2, the author was making the assumption that rectriction of kcal would prevent the use of insulin when insulin may be needed for adequate glycemic control regardless of the kcal level.