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  • Writer's pictureJen Curtis


This is a topic that’s been bugging me a lot lately. Like most women who are pregnant for the first time, I have been religiously devouring books and articles and blogs about pregnancy. Although my training has centred on physical activity during this time and not the pregnancy itself, I still know a fair bit about anatomy and physiology during this time of life – and it infuriates me when details are left out of some crappy blog or half-arsed book.

“Weight gain during pregnancy” is touched on a lot – and it’s almost always concluded with a variant on the following theme: “it’s normal” “try to love your body anyway, it’s doing an amazing thing” “try not to worry about the weight gain”.

Do we even need to discuss this?

Now, firstly I want to say that some people might think that it's not necessary to discuss fat gain during pregnancy – you might feel that we only need to revel in the glory of our bodies creating life and not even worry about issues such as fat gain. You might feel like it's a totally pointless topic and that I am just contributing to body image issues by even discussing it. But from my experience working with pregnant and postpartum women, I know that it's something that lots of women worry about, but they are not "allowed" to discuss it, or it is simply dismissed by literally everyone. It doesn't usually help to silence someone who is concerned about an issue, however trivial it may seem to you. It usually helps to talk about it, share the experience with others and UNDERSTAND it.

So this blog post is for those women, those that want to understand what's really going on and what the WEIGHT gain is really all about.


As a trainer, when people talk about wanting to lose weight, we are encouraged to talk to them about losing FAT. To talk about fat-loss and fat-gain. If someone weighs 100kg and is 40% fat – there’s still a hell of a lot of mass there that ISN’T fat – there’s water and muscle and bones and skin and organs… we don’t want to lose any of that weight. Women are often obsessed with the WEIGHT on the scale and want it to go down no matter what, but they aren’t paying any attention to, or measuring in any way how much of that is FAT. It is critical if we want to keep our metabolism up and stay strong and achieve long-term fat-loss.

It’s a similar story with pregnancy. Yes, you are going to gain weight, and yes it is normal. It is also very disconcerting if you’ve watched your weight for a long time to see it creep up on the scales.

But most books, when they address it in the way that I described above, make it sound like you have to deal with a whole lot of FAT gain – and this isn’t necessarily so – there is a whole lot of matter being made by your body at this time, and fat isn’t necessarily a large part of it (although it will be for some women).

Over the course of a normal pregnancy, you are likely to add weight in the following ways:


3-4 kg

This is no surprise to people

Amniotic fluid

0.5 kg


1 kg

Yes, 1kg, just uterus, NOT it's contents. The uterus of a woman who has never had a baby weighs approximately 100g. During pregnancy, it undergoes MASSIVE growth to accommodate the baby (it doesn't just stretch.) By the end of pregnancy it weighs around 1.1kg


1-2 kg

The average woman has around 4 litres of blood before pregnancy. At the beginning of pregnancy, her blood vessels dilate and her body has to produce more blood to fill the space (a problem called "underfill", which I will address in detail in another post). The result is a massive 40% increase in the total volume of blood in the woman's body. That's sometimes as much as 2 litres, or 2 kilos - just of blood! This helps supply the foetus with nutrients and oxygen all the time, dissipate heat and gives her a cushion in the event of blood loss. If combined with cardiovascular exercise, it can massively improve her cardiovascular fitness (an effect similar to blood doping). Again, I will discuss this more at length in a future post.


0.5 -2 kg

A large portion of this is not actually FAT gain. The mammary glands grow and expand in size and weight (and number too, I believe). This obviously varies quite a bit from woman to woman.


1 kg

In addition to all the extra blood that we produce, the body retains a lot of extracellular fluid. Water accumulates in and around the cells of the body. This too varies from woman to woman, but on average we retain about a litre (1kg) of extra water in our tissues.



When you add up all these numbers, it totals around 10-11kg before we've added any fat whatsover.

I think all of this is amazing, I do, inconvenient, but amazing, BUT I also find it comforting to know that all of this weight-gain is not fat. My body is in a frenzied state of anabolism (growth) – it’s taking raw materials from the food I eat, from the oxygen I breath, from vitamins and minerals I have stored in my body, and it’s turning it into mass, matter, organs– it’s building tangible stuff that wasn’t there before. For my, logical, rational brain, THAT is what I need to know. That soothes the anxiety about weight gain, because I know that it’s unavoidable, you can’t make all that stuff without it weighing something. And it’s unlikely that much of it is fat.


It's important to note that these changes result in an increase in metabolic rate, that increases throughout pregnancy. Metabolism is not understood by most people (and I will write a separate blog post on the topic) but you can understand it simply as the total sum of energy consumed by the body's cells to carry out functions (like breathing, digesting, absorption, cell repair etc).

The increase in matter causes an increase in metabolism in the following ways:

  1. As I said above, the body is in a frenzied state of anabolism (growth). it’s taking raw materials from the food I eat, from the oxygen I breath, from vitamins and minerals I have stored in my body, and it’s turning it into mass, matter, organs, tissues, cells – it’s building tangible stuff that wasn’t there before. This "costs" energy – just like you would have to feed workers for them to have the energy to build a house, to obtain and carry the materials, put them together etc. So metabolism goes up.

  2. The body then has to MAINTAIN this new material – as stated before, this is all LEAN MASS, active tissues that have functions, which they require energy to perform – they also require energy (glucose, oxygen) to just exist. This raises the metabolic rate, i.e. more energy is being used to build new material and then maintain said material. We use calories to measure energy.

  3. You then have to carry the increased weight around. So let's say that at the six month mark, a woman is 6 kilos heavier – her muscles, particularly in her legs, but everywhere, have to work harder to carry this weight around that it was not previously carrying. We know this intuitively: think of climbing up a hill with just the clothes you are wearing – then think of climbing the same hill with a 6kg rucksack – your heart rate would go up faster (because there is more "work" being done in the tissues and so the body has to supply those tissues with more blood to give it nutrients to do said work and get rid of waste products. This is an example of increased metabolism - the body requires more calories to do the task, much like a bigger car would require more fuel). Again, this is a separate topic and I will expand on it in a future post.

Metabolism during Pregnancy.

What I have described above is the ways in which our basal metabolic rate (BMR) increases during pregnancy - that the body is GROWING another human then carrying it and all the supporting infrastructure around all day. These processes require energy (which is ultimately what metabolism is - the total amount of energy for each of our physiological actions).

Most women now know that "eating for two" is a myth and that we use nowhere near that amount of energy - but nowadays we do have some numbers to give us a better idea. The Academy of Nutrition and Dietetics give us the following figures

First trimester - generally, women do not require any additional calories

Second trimester - metabolic rate increases on average by 340 calories a day

Third trimester - daily calorie requirements increase by about 450 calories above baseline

Breastfeeding - daily calorie requirements increase by about 500 calories above baseline

This means that your body is using (or "burning") something like the extra figures listed above. So if a woman requires 2000 calories a day to maintain her weight when she's not pregnant, as she progresses through her pregnancy she will be using more and more calories every day, and so will need to take those extra calories in through food in order to not lose weight - and, of course, to provide the nutrients and energy that she needs to make the damn baby!

As your metabolic rate increases, so does your appetite (i.e. you feel hungrier).

This is important to remember, since many women panic - I hear all the time "I'm eating so much, I'm going to get so fat!". It does feel like you're eating a lot, but it's important to remember that that increased sense of hunger has a reason. More calories are actually needed. THAT is why your hunger is going up. Most women have this notion that they are way hungrier and so are eating more, and that must just be turning into fat. This is not the case. (People also love to say "it's the hormones", which really grinds my gears.)

Obviously there is an upper limit to how many calories you can consume. Lets take the example of a woman who needs 2000 calories a day when not pregnant in order to maintain her weight. She is now in her third trimester. 2000 + 450 = 2450. If you need 2450 calories a day, and consume 3450 calories a day, you will store the extra 1000 calories as fat. This is why "eating for two" is inaccurate. (It's more like eating for 1.2 or something!)

Getting back to weight gain...

So imagine that your body is taking the food you eat, breaking it down through the process of digestion into all the building blocks of life - fat, carbs, proteins and vitamins and minerals. These nutrients are then shipped off to your entire body (as they do all the time) to fuel movement and metabolic processes, and to provide the raw materials to carry out those metabolic processes.

But now there is a whole bunch of NEW metabolic processes going on in and around the womb (and other places too, like your cardiovascular system). Nutrients and all those little building blocks are being shipped to the womb and converted into new material: a placenta, more womb, and a baby! These processes cost energy, but the resulting new matter WEIGHS something.

To illustrate my point…

So from where I was standing at 4 months pregnant (when I started this blog post), having gained about 2 kilos, I was not in the slightest bit worried that I had gained lots of fat. Probably at least HALF of that was likely JUST BLOOD! (Not to mention that a far bit of weight gain in the first trimester is usually due to water retention). On top of this, my belly was starting to show somewhat, but the rest of my body hadn’t changed an awful lot (apart from the fact that I had lost some muscle, which would offset some of the increases in metabolic rate, but that's another matter entirely). I also knew that my uterus was the size of a grapefruit and there was a baby in it which at that stage was quite a few centimetres long. I had a placenta by then (I had never had one of those before)… so one or two kilos makes sense, and knowing this meant that I was not freaking out about fat gain (although, even if the 2 kg had been all fat gain – that also isn’t a huge amount and it isn’t the end of the world).

4 moths pregnant

8 months pregnant

I'm finally finishing this blog post at 32 weeks (so many plans for my pregnancy, things I wanted to "finish before the birth" – ha! I totally didn’t account for pregnancy just taking time and energy!) I'm 10kgs up, and I'm definitely starting to gain some fat, but still, I'm not worried. I can't imagine that it's more than a couple of kilos, both if you do the maths and by looking at me.

The following two pictures were taken around 36 weeks, by which time I was up 13 kgs. While this is starting to get towards the upper end of the range for healthy weight gain during pregnancy, and I still have a few weeks left, I'm still not freaking out about fat gain.

It's incredibly difficult to measure body fat at this time, but ultimately you can see from the pictures below that the rest of my body has not changed hugely, and I have not put on huge amounts of fat - using this metric (how you look) along with body weight is probably the best way to gauge fat gain.

Do we even need to gain fat during pregnancy?

Now most women do put on at least some fat during pregnancy, and that’s totally normal – but I work with many women who don’t actually gain any fat during their pregnancies, or who gain a little, and it comes straight off, or who lose it while breastfeeding, who only lose it after they stop breastfeeding, or who gain a little or a lot after giving birth. It’s all normal, and I assume that it largely depends on a mixture of the following factors:

  1. Did pregnancy give you nausea? Did it make it hard to eat? Was it just the first trimester? Or did you feel sick right the way through? It’s likely that it was hard to get the calories you would need for significant fat gain if this was the case.

  2. How did you respond to that nausea? Did you eat less overall? Or did you still eat a lot, but just junk and palatable, high-calorie foods. Some women won’t be able to get enough calories in, some will go a bit bananas on the less healthy stuff that they can eat.

  3. How do you respond to stress and fatigue with food? Are you a comfort eater? Or do stressful situations and anxiety make you lose your appetite? Some people will respond to fatigue by wanting to eat everything, others “can’t be bothered” to eat.

  4. How stressed/anxious/fatigued were you during pregnancy? Some women don't experience any of these symptoms (I hate them a bit).

  5. Did you have your weight and food intake under control before pregnancy? Or did you have an erratic approach to food and weight-loss. It’s likely that if you were yo-yo dieting for a long time, pregnancy might be a bitter-sweet relief from obsessing about food, and you may relish the opportunity to eat "whatever you want".

  6. Genetics

  7. How much exercise did you do during your pregnancy? This will help for 3 reasons

  8. (most obviously) it adds to calorie expenditure and will help you maintain valuable muscle mass (which will contribute to overall metabolic rate (how many calories you burn a day)).

  9. It will improve or maintain your fitness, which affects the physiology of your whole body, and will make everything work better.

  10. It can be a powerful tool for lifting your mood, increasing your motivation and relieving symptoms like nausea. It can be a relaxation method for many women, and just as some women will grab a treat or a glass of wine to soothe their discomfort (emotional or physical) some women have built the habit to do this through other means, like going for a run or swim, lifting weights (and others use techniques like meditation, which won’t improve our physiology in the same way, but can also soothe negative experiences)

  11. Did you have gestational diabetes? Many women are forced to go on a "diet" to control the GD and so find it impossible to gain fat (or even lose some).

  12. How much body fat did you have before getting pregnant?

  13. If you (like me) were pretty lean (<20% body fat) it's likely that you will put some fat on during pregnancy (and this is probably healthy and natural – the body is designed to store a bit more fat to have a backup energy supply).

  14. Maybe you are naturally thin – many women like this don't actually put on any fat, or very little.

  15. If you were carrying excess body fat beforehand, you could lose some of it during pregnancy, or perhaps be more prone to put some more on (habits and lifestyle will play a role here, not just genetics)

There are probably lots of other factors too, but these are the things that immediately spring to mind for me, remembering that I’m coming from a perspective of nutrition, eating disorders, disordered eating, lifestyle and exercise. Throughout much of my career I’ve been helping women overcome issues with food, trying to establish a healthier relationship with food and helping them achieve lasting fat loss. Over the years I have realised more and more how psychology plays a humongous role in fat loss and weight management, more than most people realise – and I expect we carry much of that with us into pregnancy.

This list is not intended to be totally comprehensive. My aim here is to illustrate how complex the issue is, how many factors may be involved, and how intertwined those factors can be.

Bottom line however, it's pretty hard to control fat gain during pregnancy. There are so many factors dictating at this time. Some fat gain is probably healthy, yet there's no need for alarm if you don't put on any fat. It ISN'T something that we should be trying to control (beyond ensuring that we don't put on huge amounts of weight, which also isn't healthy).

Lets keep some perspective…

Fat gain during pregnancy is going to vary from woman to woman, there’s no doubt about that. But there’s no doubt about it that a large amount of fat-gain is not only unnecessary, but it may be unhealthy. The 11+ kilos of the weight we will gain during pregnancy is going to be STUFF that can’t be avoided. For most women, a few kilos of fat gain will be totally normal, so if you weigh something like 16kg more the day before you give birth than you did before pregnancy, you may have gained something in the region 5kg of fat (or none at all). 5kg of fat is NOT a big deal (some women talk as if they’ve gained 16kg of fat). If you were a healthy weight before pregnancy you will feel it, yes, and that will probably suck a bit, and you probably won’t like the way it looks.

Implications for postpartum "weight" loss.

Let's start with fat loss. If you have only put on a modest amount of fat, it really isn't a big deal in the grand scheme of things, and how quickly it comes off may depend on a lot of factors, including genetics.

The popular scenario of it just melting off while breast feeding, while absolutely true for some women, isn't the case with others. Many women I work with feel disappointed because their friend/sister/colleague "got skinny" while breastfeeding and they have either stayed the same or put on more fat. For reasons that we don't understand, this part of the process is different for anyone, and if you are struggling with your weight while breastfeeding, it's really important that you know that it's totally normal, and many women experience fat loss only after they stop breastfeeding (incidentally, this can sometimes be the same for improvements in diastasis recti and pelvic floor complaints.)

Moreover, it's not just about fat loss. Most women have the expectation that the belly will just go back to what it was before pregnancy, overnight. This is a totally unreasonable expectation! For the following reasons:

  1. It will take time for the body to break down a lot of the tissues it had made during pregnancy. Ok, so you've removed the baby, placenta and amniotic fluid from the equation (around 4-6kg of "stuff"), but the uterus still weights 1.1kg (or thereabouts) and needs to shrink back down to 100g. This will take some time! The body now needs to break down a KILO of tissue that it no longer needs, and in the meantime, there is still going to be a belly as a result.

  2. The abdominal muscles have been stretched over 9 months to accommodate A LOT of extra stuff. They do not and cannot spring back to where they were before. Ok, so some of that stuff has been removed, but the weight of the abdominal organs are now pressing against the abdominal muscles that have less tone in them than they had before. It will take time for these muscles to regain tone and push the abdominal organs back inwards and upwards.

This is important to understand when we are coping with body image and our postpartum body, when we still have that “tummy” and we don’t know why (“but the baby’s out!”) – knowing that there is still a lot in there that the body needs to deal with, and it isn’t a process that can be hurried along – that has huge implications for the post-partum woman (but it’s also a separate blog post).

How do you track fat gain during pregnancy?

It can be difficult to track fat accurately during pregnancy (or at any time). I did an “InBody” scan at the beginning of my pregnancy and plan to do another one soon to see how much fat I gain/muscle I lose, but that isn’t an option for everyone. (It also isn't particularly accurate as it will show gains in lean tissue too… so even if I gain fat, my body fat percentage may still be lower because it is offset by all the other stuff). You can also use a caliper, but otherwise, you will have to rely on a rough guestimate – assuming that 11-ish kilos are non-fat-gain, any weight you gain over that may be fat (you may also have a bigger baby, more blood, more fluid retention, etc – but that’s why it’s a guestimate). Being totally anal and 100% accurate isn’t necessary – we just need a rough figure. (We don't even "need" a rough figure, but I think most women find it helpful in order to put things in perspective).

Knowing this information is crucial I feel for calming our minds. Nowadays, we don’t just want a doctor to tell us “it’s normal” – or a blog post to tell us “it’s beautiful, embrace your fuller form!” – we want to know, we want to understand, we want to have someone appeal to the rational part of our brain, so here was my attempt to appeal to yours…

I’ve got some incredible content on the gram for you

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