Is it recommended to lose weight during pregnancy if you are obese?

Weight Loss During Pregnancy in Obese Women

Weight loss during pregnancy is not recommended for obese women, even those with severe obesity. The focus should be on controlling weight gain within recommended limits rather than attempting weight loss. 1

Primary Recommendation: Weight Control, Not Weight Loss

The evidence is clear and consistent across multiple clinical practice guidelines:

• Two clinical practice guidelines explicitly state there is no evidence to recommend weight loss during pregnancy. 1
• The goal for obese pregnant women is to control and limit gestational weight gain according to Institute of Medicine (IOM) guidelines, not to lose weight. 1
• Thirteen guidelines emphasize the importance of controlling weight during pregnancy through diet and exercise counseling, but this means preventing excessive gain, not promoting loss. 1

Exception: Medical Considerations Only

Only one guideline suggests weight loss might be considered, and this is strictly limited to specific medical indications:

• Weight loss during pregnancy should be based solely on co-existing medical conditions such as diabetes or hypertension that require intervention. 1
• This is not a general recommendation but rather a case-by-case clinical decision for women with serious comorbidities. 1

What Should Be Done Instead

Preconception Weight Management

• Weight loss should occur BEFORE pregnancy, not during. Thirteen guidelines recommend stabilizing weight or achieving weight loss before conception. 1, 2
• Women with obesity should receive counseling about the benefits of pre-pregnancy weight reduction for improving maternal and fetal outcomes. 2, 3

During Pregnancy: Focus on Appropriate Weight Gain

• Provide diet and exercise counseling at the first prenatal visit based on BMI and IOM recommendations. 1
• Target 30 minutes of moderate-intensity exercise daily or 150 minutes per week. 1
• Offer nutritional consultation and dietitian referral to all obese pregnant women. 1, 3
• Use gestational weight gain (GWG) counseling throughout pregnancy to prevent excessive gain. 1

Exercise Safety in Obese Pregnant Women

• Obesity alone is NOT a contraindication to exercise during pregnancy. 1
• Regular physical activity in obese pregnant women reduces risks of preterm birth and gestational diabetes without adverse fetal outcomes such as low birth weight or stillbirth. 1
• Women with obesity should complete regular prenatal physical activity within recommended guidelines. 1

Critical Pitfalls to Avoid

Risk of Inadequate Weight Gain

• Weight loss or inadequate weight gain increases the risk of small-for-gestational-age babies. 4
• Even in obese women, there must be both an upper AND lower limit for gestational weight gain to prevent negative outcomes. 4

Current Guideline Limitations

• The 2009 IOM guidelines recommending 11-20 pounds gain for obese women may be too high according to ACOG, but no weight loss is recommended as an alternative. 4, 5
• Optimal weight gain should be personalized by obesity class (I, II, III), but always within positive gain parameters, not loss. 4

Comprehensive Pregnancy Management

• Focus on preventing obesity-related complications rather than weight loss: early screening for type 2 diabetes, aspirin for preeclampsia prevention (≥75 mg daily from 12 weeks if BMI ≥35), and thromboprophylaxis planning. 1
• Ensure adequate folic acid supplementation (5 mg daily) and vitamin D if deficient. 1

Clinical Approach Algorithm

1. At preconception: Strongly encourage weight loss before pregnancy through lifestyle modification. 2
2. At first prenatal visit: Calculate BMI, provide IOM-based weight gain targets, refer to dietitian, and initiate exercise counseling. 1
3. Throughout pregnancy: Monitor weight gain at each visit, reinforce dietary and exercise measures, but never recommend weight loss. 1
4. Special circumstances only: Consider weight management (not active loss) only if severe comorbidities like uncontrolled diabetes or hypertension require intervention. 1

The evidence consistently prioritizes maternal and fetal safety over weight reduction during pregnancy, as inadequate gestational weight gain—even in obese women—carries significant risks for fetal growth and development. 1, 4