Can I Lose Weight in the First Trimester? What to Know

Losing weight during pregnancy is generally not recommended, regardless of your starting weight. Attempting to lose weight or dieting while pregnant could mean you miss out on essential nutrients vital for your health and your baby’s development. However, many women wonder, Can I Lose Weight In The First Trimester? There is a specific exception regarding the early weeks of pregnancy where some weight loss might occur and is often not a cause for concern. Understanding why this happens and when to seek advice is crucial.

The relationship between maternal weight changes and fetal health during pregnancy is complex and still under investigation by experts. However, actively trying to lose weight is generally considered incompatible with supporting healthy fetal growth. If you are losing weight, particularly outside the very early stages, it might indicate you aren’t consuming enough calories and nutrients necessary for a healthy pregnancy outcome. While being overweight or obese during pregnancy does carry increased risks for certain complications, deliberately losing weight can increase the risk of having a baby that is small for gestational age (SGA) or born prematurely.

Pregnant woman sitting thoughtfully on a park bench while looking at her phone, considering first trimester changes.

Why Might Weight Loss Occur in Early Pregnancy?

It can be quite normal to experience some weight loss during the first trimester. Common reasons include:

• Morning Sickness: Nausea and vomiting are frequent symptoms in early pregnancy. This common condition, known as morning sickness, can significantly reduce appetite and lead to calorie loss through vomiting, sometimes resulting in weight loss. Rest assured, during this early phase, your baby typically still receives all the necessary nutrients.
• Using Fat Reserves: Women who start pregnancy overweight or obese have additional calorie reserves stored as body fat. As the baby begins to grow, drawing on these reserves might lead to maintaining or even slightly decreasing weight initially without harm.
• Lifestyle Improvements: Discovering you’re pregnant often prompts positive lifestyle changes. If you’ve recently started a gentle exercise routine or adopted healthier eating habits, you might naturally lose a small amount of weight early on.

In most instances, this early weight fluctuation isn’t dangerous. However, if you experience significant weight loss or suspect you might have hyperemesis gravidarum (a severe form of morning sickness), it’s important to inform your healthcare provider immediately.

Weight Gain Guidance if You Are Overweight or Obese

Starting pregnancy with a higher body mass index (BMI) is common; more than half of pregnant women in some populations are classified as overweight or obese.

You are considered overweight if your pre-pregnancy BMI is between 25 and 29.9. Obesity is defined as a pre-pregnancy BMI of 30 or higher. Your BMI is an estimate of body fat based on your height and weight.

The recommended amount of weight gain during pregnancy varies based on your starting BMI:

• BMI 25 to 29.9 (Overweight): The general recommendation is to gain between 15 and 25 pounds total, aiming for about 2 to 3 pounds per month during the second and third trimesters.
• BMI 30 or higher (Obese): The recommendation is typically to gain between 11 and 20 pounds throughout the pregnancy.

While actively losing weight is unsafe, if you are overweight or obese, gaining less weight than the standard guidelines might be safe under the careful supervision of your healthcare provider. The Institute of Medicine (IOM) provides these guidelines, though there has been some discussion regarding the recommendations for obese women, particularly as they offer a single range for all BMI levels above 30.

Some research suggests that overweight or obese women who gain slightly less than the IOM recommendations (e.g., 6 to 14 pounds) may experience similar or even better outcomes for their babies compared to those who gain within the recommended 15 to 20-pound range. Discuss your personal weight gain target with your provider. They will monitor both your health and your baby’s growth closely if you gain less than the standard recommendation.

Why Dieting During Pregnancy Is Unsafe

Pregnancy is unequivocally not the time for restrictive weight-loss diets, irrespective of your starting weight. Limiting your food intake can be hazardous for both you and your developing baby, as you both require sufficient calories and a wide range of nutrients.

Avoid carbohydrate-restrictive diets like keto or Atkins during pregnancy. Your growing baby needs carbohydrates for development, and the state of ketosis these diets induce can potentially harm a fetus.

Instead of dieting, focus on managing weight gain healthily through balanced nutrition and regular, appropriate exercise. Aim to:

• Eat well-balanced meals and choose healthy snacks.
• Stay well-hydrated, drinking around ten 8-ounce glasses of water daily.
• Prioritize complex carbohydrates (beans, fruits, vegetables, whole grains) over simple carbs (white bread, white rice, white pasta).
• Regularly monitor your weight gain progress with your healthcare provider.

Weight Loss During Pregnancy: Warning Signs

While some weight loss in the first trimester might be normal, losing weight during the second or third trimester can indicate an underlying issue. Sometimes it might be harmless, perhaps due to shedding retained water weight. However, it’s crucial to report any weight loss during these later stages to your healthcare provider.

Your provider will evaluate your diet, activity levels, and ask about symptoms like nausea, heartburn, bloating, or constipation, which can understandably affect appetite. They might also screen for conditions such as depression or assess for fetal growth restriction.

Contact your provider immediately if you experience sudden, dramatic weight loss, such as losing five pounds within a single week.

Conclusion

Losing a small amount of weight in the first trimester is often normal due to factors like morning sickness or adopting a healthier lifestyle. However, actively dieting or losing significant weight at any stage of pregnancy is generally unsafe and not recommended. If you started your pregnancy overweight or obese, work closely with your healthcare provider to establish a suitable weight gain target, which might be slightly less than standard guidelines under careful monitoring. Focus on balanced nutrition and appropriate exercise rather than restrictive dieting. Always report any significant or concerning weight loss, especially after the first trimester, to your provider promptly to ensure the well-being of both you and your baby.

References

ACOG. 2021. Nutrition during pregnancy. American College of Obstetricians and Gynecologists. https://www.acog.org/womens-health/faqs/nutrition-during-pregnancy [Accessed August 2021]

ACOG. 2021. Obesity and pregnancy. American College of Obstetricians and Gynecologists. https://www.acog.org/womens-health/faqs/obesity-and-pregnancy [Accessed August 2021]

ACOG. 2020. Weight gain during pregnancy. American College of Obstetricians and Gynecologists. https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2013/01/weight-gain-during-pregnancy [Accessed August 2020]

IOM. 2009. Weight gain during pregnancy: Reexamining the guidelines. The National Academies Press, Washington D.C. https://www.ncbi.nlm.nih.gov/books/NBK32813/ [Accessed August 2021]

Kapadia MZ et al. 2015. Weight loss instead of weight gain within the guidelines in obese women during pregnancy: A systematic review and meta-analyses of maternal and infant outcomes. PLoS One 10(7): e0132650 https://pubmed.ncbi.nlm.nih.gov/26196130/ [Accessed August 2021]

March of Dimes. 2020. Being overweight during pregnancy. https://www.marchofdimes.org/pregnancy/being-overweight-during-pregnancy.aspx [Accessed August 2021]

Rasmussen KM et al. 2010. Recommendations for weight gain during pregnancy in the context of the obesity epidemic. Obstetrics & Gynecology 116(5): 1191-1195. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4288953/ [Accessed August 2020]

Robillard PY et al 2018. Relationship between pre-pregnancy maternal BMI and optimal weight gain in singleton pregnancies. Heliyon 4(5) E00615. https://www.cell.com/heliyon/fulltext/S2405-8440(18)30300-1 [Accessed August 2021]

Siega-Riz AM et al. 2009. A systematic review of outcomes of maternal weight gain according to the Institute of Medicine recommendations: birthweight, fetal growth, and postpartum weight retention. American Journal of Obstetrics and Gynecology 201:339. E1-14. https://pubmed.ncbi.nlm.nih.gov/19788965/