How Much Does Metabolism Increase During Pregnancy?

Your metabolism does not stay the same during pregnancy. It rises. By the third trimester, your basal metabolic rate increases by about 15 to 20 percent. This means your body burns roughly 300 extra calories each day in the second and third trimesters to support your growing baby and the changes in your own body.

What Is Metabolism and Why Does It Matter in Pregnancy?

Metabolism is the process your body uses to turn food into energy. Even when you are resting, your body burns calories to keep your heart beating, your lungs breathing, and your cells working. This baseline energy burn is called your basal metabolic rate (BMR).

During pregnancy, your body is building new tissue — the placenta, the baby, extra blood, and more. All of this requires energy. So your BMR goes up. Understanding how much metabolism increases helps you know how many calories you actually need, which can prevent unnecessary weight gain or inadequate nutrition.

How Much Does Metabolism Increase During Pregnancy?

Metabolism does not jump up all at once. It rises gradually across the three trimesters. Research consistently shows that BMR increases by roughly 10 percent in the first trimester, 15 percent in the second, and 20 to 25 percent in the third. For most women, that translates to an extra 300 calories per day during the second and third trimesters.

These numbers come from well-established studies on energy expenditure in pregnancy. They are used by organizations like the American College of Obstetricians and Gynecologists (ACOG) to guide weight gain recommendations. The exact increase depends on your starting weight, activity level, and whether you are carrying one baby or more.

Why Does Metabolism Increase During Pregnancy?

Several factors drive the rise. First, your heart works harder. Your blood volume increases by about 50 percent, so your heart pumps more blood each minute. That uses more energy. Second, your breathing rate increases to supply oxygen to you and your baby.

Your body also builds new tissues. The placenta is metabolically active — it uses glucose and oxygen to support the baby. The baby itself is growing, and fetal tissues require a steady supply of energy. Additionally, your kidneys work harder to filter the extra blood, and your gastrointestinal tract slows down to absorb more nutrients.

All of these changes add up. By the third trimester, your body is essentially running a continuous low-grade extra workload. That is why your resting metabolism is significantly higher than before pregnancy.

How Does the Metabolism Increase Affect Your Calorie Needs?

The common advice “eating for two” is misleading. You do not need double the calories. In the first trimester, most women need little to no extra calories — only about 100 extra calories per day, which is easily covered by a small snack. The real increase comes in the second and third trimesters.

For a woman who started pregnancy at a healthy weight, the extra energy need is about 340 calories per day in the second trimester and 450 calories per day in the third. That is roughly equal to an apple with peanut butter, a yogurt with berries, or a small sandwich. These extra calories should come from nutrient-dense foods, not empty calories.

If you are underweight before pregnancy, you may need more. If you are overweight or obese, your doctor may recommend a smaller calorie increase. Always follow your specific healthcare provider’s guidance, because individual energy needs vary.

Does Metabolism Increase Differently for Different People?

Yes. Several factors influence how much your metabolism rises. Pre-pregnancy body size plays a role. Women who are heavier at the start tend to have a smaller percentage increase because their baseline BMR is already higher. Women who are very lean may see a larger relative jump.

Age also matters. Younger women generally have a higher BMR, and the pregnancy-related increase may be somewhat greater. Carrying twins or triplets raises the energy demand further — studies show that BMR can increase by 30 to 40 percent in twin pregnancies. Physical activity level also affects total calorie needs, but the BMR rise itself is relatively consistent across different activity levels.

What Happens to Metabolism After Childbirth?

After delivery, your metabolism begins to drop back toward pre-pregnancy levels. The placenta is gone, and your blood volume decreases. But the change is not immediate. If you breastfeed, your metabolism stays somewhat elevated — about 300 to 500 extra calories per day are needed to produce milk.

Many women find that their metabolism does not return completely to baseline for several months. This is normal. Weight loss after pregnancy takes time, and calorie needs gradually decrease as breastfeeding frequency reduces and your body recovers. Rapid weight loss is not recommended, especially while nursing.

Can You Influence Your Metabolism During Pregnancy?

You cannot change the fundamental rise in BMR — it is a biological necessity to support your baby. However, you can support a healthy metabolism through lifestyle choices. Eating enough protein helps maintain muscle mass, which supports a higher metabolic rate. Staying active with prenatal-approved exercise — such as walking, swimming, or pregnancy yoga — can also help manage weight gain and keep your metabolism functioning well.

Avoid crash diets or severe calorie restriction during pregnancy. Restricting calories too much can actually slow your metabolism and deprive your baby of essential nutrients. The goal is to eat enough to meet the increased energy needs without overshooting.