Understanding Calories + Weight During Pregnancy

Pregnancy is a metabolically demanding time, and our body, appetite, and energy undergo continuous changes in response to the needs of the growing baby. And whilst it’s important to embrace these changes, some of the things that women can often feel most anxious and in the dark about are what to eat, how much to eat, and how much weight gain is normal. A survey by the National Charity Partnership (NCP) of 2100 women in the UK revealed that 61% of the pregnant women surveyed thought they needed more than the recommendations. 

Both nutrient status and gestational weight gain (or lack thereof) can have significant and long-lasting effects on the health of both mama and baby, but despite their importance, little to no nutrition or lifestyle counselling is given to women throughout pregnancy and the postpartum period. So, how many calories do we actually need? And what does ‘healthy’ weight gain look like? Let’s dive in.  

Calories in Pregnancy.  

This may come as a surprise, but calorie requirements during pregnancy increase far less than most of us think. The American College of Obstetrics and Gynaecology (ACOG) guidelines suggest that in the first trimester, no extra calories are required, whereas other governmental bodies recommend up to 200kcal per day. To put it into context, this would be akin to a medium sized apple with about 1tbsp of almond butter.  In the second and third trimesters, ACOG recommends 340kcal and 450kcal per day for single pregnancies, and 600kcal per day for multiples. (1) 

But for many of us, these recommendations feel completely counterintuitive, especially because it’s not uncommon to feel – let's face it - ravenous throughout the first trimester and beyond. To be told that we don't need the calories we’re craving can be incredibly disheartening and can also induce anxiety that there may be something inherently wrong with us if an extra apple a day won’t cut it.  

The reality, of course, is more nuanced, and will depend on a variety of factors. These include, but aren’t limited to:   

Calories vs Nutrients.  

Perhaps more important than total calorie intake, however, is total nutrient intake. When we focus on nutrients, we’re less likely to consume empty calories, and we can feel more confident that we’re meeting the needs of our baby and the demands of pregnancy.   

As an example, let’s look at protein. Protein requirements increase considerably during pregnancy; in addition to its role in foetal development and maternal tissue growth, we also know that it plays a key role in satiety signalling and appetite control. A 100gr chicken breast boasts 165kcal, 30g of protein, and a hefty dose of Choline (essential for foetal development), Vitamin B3, and Vitamin B6, whereas a 40g pack of crisps has a similar calorie count (200kcal) but 0g protein, little to no contribution on the vitamin and mineral front and is predominantly empties carbohydrate with unhealthy fats and salt.  

For those who avoid animal protein, a similar comparison can be made with plant-based options; a 1 cup serving of pinto beans delivers 245kcal, 15g of protein, 15g of fibre, and a good amount of calcium, magnesium, potassium and folate. Because of their nutrient density, the whole food examples, whether animal or plant based, would also promote satiety, a feeling that most pregnant women are striving for. 

Using nutrient density and food quality as a guide rather than total calories, it becomes easier to make food choices that have nutritional benefits rather than having a simple calorie goal without understanding how they may be contributing to how we feel. Focusing on good quality food doesn’t mean that we should avoid indulging – and some pregnancy cravings are just too strong to ignore! – but being mindful of what we’re regularly eating during pregnancy will help support both maternal and foetal wellbeing.  

How much weight gain is normal? 

Weight gain and pregnancy can be a triggering topic and feel overwhelming for many, especially for those with a history of body image issues, disordered eating, or who have been victims of body shaming. And whilst it can be helpful to use the guidelines as a reference range, it’s important to have a more holistic view that incorporates exercise, nutrition choices, and stress management rather than having a sole focus on the number on the scale. Before we dive into the recommendations, let's go through why we gain weight in the first place.  

Why we gain weight.  

To get comfortable with healthy weight gain in pregnancy, it can be helpful to understand what's actually going on in our bodies. In addition to the weight of the baby, weight gain during pregnancy can be attributed to the following (amazing) adaptations: 

This accounts for over 10kg, without even factoring in the weight of the baby. Naturally, total weight gain will vary depending on maternal height, pre-pregnancy body composition, level of activity, and other factors, but you can see from these numbers how important it is to embrace the changes that are happening in your body during pregnancy rather than fear them.  

Recommendations for the appropriate amount of weight gain vary by country and culture, and the U.K., there are no official guidelines on weight ranges. The guidelines that serve as the most accepted are those recommend by the Institute of Medicine (IOM), which lays out healthy weight gain ranges that differ by pre-pregnancy BMI: 

Source: ACOG committee on Obstetric Practice, adapted from IOM.  

There are some drawbacks to using BMI alone as a measure of health. Pre-pregnancy BMI, which is a calculation of our weight relative to our height, can be influenced by ethnicity and muscle mass, and doesn’t account for other factors such as genetic predispositions or fat distribution. Fat distribution, for example, is an important predicator of metabolic health. For example, we could have a normal BMI but excess visceral fat (the dangerous type of fat around our belly and internal organs), which would represent an increased health risk compared to someone who perhaps has a higher BMI but little to no visceral fat.  

Although BMI on its own isn’t an entirely accurate measure of overall health, it is independent predictor of various adverse outcomes during pregnancy. (3) There is often a focus on excess body weight, but adverse maternal and infant outcomes are associated with both inadequate weight gain and excess weight gain when compared with weight gain within the recommended levels. What are the risks?  

Most common risks of inadequate weight gain include: 
- An increased risk of preterm birth 
- An increased risk of SGA baby (small for gestational age)  

Most common risks of excess weight gain include: 
- An increased risk of gestational diabetes (GDM)* 
- An increased risk of preeclampsia  
- An increased risk of preterm birth 
- Increased risk of macrosomia (large baby) 

Weight gain can be one indicator of whether we’re getting adequate nourishment during pregnancy, but it’s not the only indicator, and as such, should only be considered alongside other markers of health. In fact, pre-pregnancy metabolic health is more closely associated with adverse outcomes than weight gain alone during pregnancy. (4) This is why it’s important, whenever possible, to optimise lifestyle factors like nutrition, exercise, and a good quality pre-natal supplement as early as possible in the reproductive journey. 

Our bodies are unpredictable; some of us will remain active and follow a healthy diet that is low in sugar and ultra processed foods, with adequate micronutrients and calories, and still gain weight over or under the recommended guidelines. It's important not to be overly worried; everyone is unique, and the level of nourishment is more important than the ultimate number on the scale, unless your doctor advises you otherwise.  

- Be kind to yourself, our bodies are capable of amazing things, and so prioritising a healthy and accepting approach to the changes that occur is important

- Seek support. Knowledge is power, so if you're worried about how to approach nutrition during pregnancy, consult with a specialist nutritionist, dietician, or professional. 

- Prioritise whole food and reduce added sugar. This simple steps will deliver more nutrients, support healthy energy levels, and help you feel more balanced. Try a Mediterranean style diet, which includes healthy protein from a variety of sources, healthy fats, lots of fibre, fruit, and vegetables.   

When to seek medical advice.  

There are some instances in which weight can be a proxy for an underlying issue that should be addressed by your doctor. Here’s what to look out for:

If you experience any of the following, or if you are worried about anything at any time during your pregnancy, it's important to seek medical advice. 

Article adapted from: Nutrition for Fertility + Pregnancy ebook, which includes nutrition guidelines, expert recommendations, and over 50 fertility friendly recipes. The ebook is complimentary with every purchase of Enhanced Fertility. 

Disclaimer: The information presented in this article is for educational purposes only and is not intended to diagnose, prevent, or treat any medical or psychological conditions. The information is not intended as medical advice, nor should it replace the advice from a doctor or qualified healthcare professional. Please do not stop, adjust, or modify your dose of any prescribed medications without the direct supervision of your healthcare practitioner. 

References: 

1. ACOG. https://www.acog.org/womens-health/faqs/nutrition-during-pregnancy#:~:text=During%20the%20first%20trimester%20with,%2C%20yogurt%2C%20and%20fresh%20fruit. 
2. https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2013/01/weight-gain-during-pregnancy 
3. Institute of Medicine (US) and National Research Council (US) Committee to Reexamine IOM Pregnancy Weight Guidelines; Rasmussen KM, Yaktine AL, editors. Weight Gain During Pregnancy: Reexamining the Guidelines. Washington (DC): National Academies Press (US); 2009. 7, Determining Optimal Weight Gain.
4. LifeCycle Project-Maternal Obesity and Childhood Outcomes Study Group. Association of Gestational Weight Gain With Adverse Maternal and Infant Outcomes. JAMA. 2019;321(17):1702–1715. doi:10.1001/jama.2019.3820