How many more calories do you burn when pregnant

New research is shedding light on calorie consumption and calorie burning in early pregnancy in women with obesity, which could inform strategies to promote healthy gestational weight gain and reduce racial disparities in pregnancy outcomes. Because of increasing rates of obesity, larger numbers of women than ever before are entering pregnancy with obesity. Pregnant women with obesity are more likely to have excess gestational weight gain. They are also at higher risk of developing other complications, such as gestational diabetes, disorders related to high blood pressure (e.g. preeclampsia) and having a baby with high birth weight. Racial disparities during pregnancy also exist. For example, pregnant African American women are more likely than White women to have complications such as gestational diabetes, preeclampsia, stillbirth, preterm birth, and weight retention after giving birth. In new research, scientists examined calorie (energy) intake and energy expenditure (calorie burning) in early pregnancy in women with obesity to identify factors that could promote healthy pregnancies and reduce racial health disparities.

Researchers studied healthy, pregnant women with obesity from different racial/ethnic backgrounds at 13-16 weeks of gestation. In their first analysis, which included data from 72 women, the researchers sought to identify factors that may influence excess gestational weight gain. They found that 88 percent of participants were sedentary, 12 percent were moderately active, and none were highly active. Furthermore, they found that energy expended during sedentary activities (e.g., rest and sleep) accounted for nearly 70 percent of the women’s daily total energy expenditure, and that energy expenditure from activity (e.g., exercise) was low. The researchers also discovered variability in the rate at which the participants burned calories regardless of their activity level: over a quarter of them had a low metabolic rate, which means they burned fewer calories than women with average or high metabolic rates and thus may have been more susceptible to excess gestational weight gain. Based on the energy expenditure measurements from their experiments, the researchers determined that the number of calories that the women should be consuming to maintain appropriate gestational weight gain was lower than what is estimated based on currently used models; those models were developed based on data primarily from women without obesity. Together, these findings identify three factors that could be contributing to excess gestational weight gain in women with obesity: current recommendations related to caloric intake during pregnancy may overestimate the needs of women with obesity, pregnant women with obesity have low activity levels, and some women have a low metabolic rate.

In their second analysis, which included data from 66 African American and White women, the researchers sought to identify biological factors that predispose African American women to worse pregnancy outcomes. They found that African American women consumed fewer calories than did White women, but there was no racial difference in physical activity levels, which were low in all women. However, after adjusting for individual differences in body weight and body composition (proportions of fat and lean mass in the body), African American women were found to burn significantly fewer calories than White women. Based on that finding and similar to results described in the first analysis, the researchers calculated that current recommendations for caloric intake during pregnancy, which do not differ by race, may overestimate the needs of African American women with obesity. Although studies have shown that African American women do not have higher rates of excess gestational weight gain than White women, it is possible that the lower energy expenditure in African American women may contribute to their higher risk of excess weight retention after giving birth—making it more likely that they will have higher levels of obesity in subsequent pregnancies. Further research to develop interventions to address the newly identified factors associated with energy expenditure during pregnancy, such as personalizing guidelines related to caloric intake and developing strategies to promote physical activity during pregnancy, could help support healthier pregnancies, reduce racial disparities, and improve health outcomes for mothers with obesity and their children.

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For the first six months of your pregnancy (first and second trimesters), you won’t need to have more calories than you did before you became pregnant. That’s about 2,000 calories a day, on average.

However, during the last three months of your pregnancy (third trimester), you will need an extra 200 calories a day, making a total of about 2,200 calories a day.

Bear in mind that we’re all different shapes and sizes, and some of us are more active than others. So any recommendation about the amount of calories you need when you’re pregnant is based on averages.

The number of calories you need while you are pregnant depends on:

• your height
• your current weight
• how active you are
• your body composition and genetics

However, you may need to adjust your calorie intake if you are expecting twins or more, or if before you were pregnant:

• your BMI was 19 or under (underweight)
• your BMI was 25 or over (overweight)
• your BMI was 30 or over (obese)

Talk to your midwife if you fall into any of these categories. She will record your weight at your first antenatal appointment. She can also tell you what a healthy weight gain in pregnancy would mean for you.

There are lots of delicious, healthy snacks you can have for an extra 200 calories in your third trimester. Here are a few ideas to get you started:

• A small, toasted wholegrain pitta, filled with a tablespoon of hummus with grated carrot and three chopped dried apricots.
• A small bowl of muesli with milk, and an apple.
• A slice of wholegrain toast, with mashed avocado or peanut butter.
• A yoghurt with a sprinkle of almonds.
• A slice of malt loaf, with cheese.

Being pregnant may sometimes make you crave fatty and sugary food. You shouldn’t go hungry, but try to get the balance right. Treating yourself to the odd packet of crisps is fine. The rest of the time, try to have healthy snacks between meals.

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These tips will help you to feel full, while keeping your calorie count under control:

• Eat breakfast every day. If you feel sick in the morning, try nibbling dry toast or crackers when you wake up. Ask your partner to bring you something before you get out of bed, and then eat the rest of your breakfast later in the morning.
• Help to control your appetite by eating high-fibre foods, drinking plenty of water, and taking regular exercise. Eat at least five portions of fruit and vegetables a day.
• Keep healthy foods to hand. A fruit bowl filled with apples, bananas, peaches, oranges and grapes makes it easy to grab a healthy snack. Also try a handful of mixed nuts, plain yogurt with a handful of berries, oat crackers with avocado dip or mashed sardines.
• Have a small amount of protein, such as lean chicken, with each meal. Balanced meals help you to feel fuller for longer.

Rather than counting calories, it’s better to eat when you are hungry, and stick to healthy foods whenever you can.

If you develop gestational diabetes and your body mass index (BMI) was 27 or over before you became pregnant, your midwife or doctor may give you different advice. She may recommend that you lose some weight by restricting the amount of calories you eat and doing more exercise. This will help to manage the levels of sugar (glucose) in your blood.

Your midwife, diabetes nurse or doctor will be able to give you more detailed advice, or you may be referred to a dietitian.

Discover more about how to have a healthy pregnancy

• Watch our video on activities to avoid when you’re pregnant.
• Check out our pregnancy weight gain estimator to see how much weight you might expect to put on during your pregnancy.
• Our trimester-by-trimester meal planners can help you make sure you’re eating the right nutrients as well as the right number of calories.

Lorna Marsh is senior editor at BabyCentre. She has more than 20 years’ journalism and editing experience, including working for the NHS.

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