3 Reasons to Ignore the Calorie/Weight Guidelines for Pregnancy

Pregnant mamas, intuitive eating is for you too.

If you ever read a book or article about pregnancy and what to expect when expecting, one of the first things you’ll see is a warning: be careful not to gain “too much” weight.

But that concept of “too much weight” is based very little on scientific and clinical outcomes, and very much on weight bias in healthcare. We live in a society that demonizes body fat, shames women for the natural size/shape of their healthy bodies, and teaches girls that one of the #1 things to fear is weight gain. This is even true during pregnancy, when weight gain is necessary for the health of mom and baby.

The most often cited recommendations for pregnant women today are to gain roughly 25-35 pounds, and to only eat an extra ~300 calories per day. Here are three reasons why I think that advice is baloney.


1. The Weight Gain Recommendations Are Flawed

The above figures for weight gain and calories are based on the Institute of Medicine’s recommendations. Their claim is that gaining above or below that range is associated with negative maternal and fetal health outcomes. I’m not disputing that. However, the large epidemiological studies that point to these associations are correlational. They don’t prove causation.

Here’s what I mean: We can see that babies and their mothers who tend to gain more or less weight than the 25-35 pound range tend to have more health problems during pregnancy and labor. However, not all women who gain more or less weight have problems. That’s because it’s not the weight that causes the problem. It’s the underlying, independent factors that cause the problem and, at the same time, cause atypical weight gain. In other words, the weight is not the cause, it’s a symptom.

In this study, which is a meta-analysis (aka one of the most powerful types of studies), the data confirm the association between atypical weight gain and health outcomes, but of the 47% of women who gain more than 35 pounds and the 23% of women who gain fewer than 25, not all of them have adverse health outcomes. (Also can we have a moment to appreciate the fact that that only leaves 30% of women who actually meet the weight gain recommendations…)

One of the most commonly stated risks of weight gain beyond the 35 pound range is gestational diabetes. As if the fact that plenty of slow-gaining women still face the unwelcomed diagnosis isn’t evidence enough, here’s the kicker: diabetes is known to cause weight gain. That’s because insulin is an anabolic hormone and when blood sugars run high and insulin secretion increases, the “build and store” function of the metabolism goes into overdrive.

Why not, instead of shaming women for weight gain, we address the causative factors behind it, such as gestational diabetes?

Here’s another problem…

What’s the point of weight gain during pregnancy, anyway? Obviously the baby weighs something, but what else is involved? Because most newborns aren’t 25-35 pounds.

Here’s what Mayo Clinic says…

  • Baby: 7 to 8 pounds
  • Larger breasts: 1 to 3 pounds
  • Larger uterus: 2 pounds
  • Placenta: 1 1/2 pound
  • Amniotic fluid: 2 pounds
  • Increased blood volume: 3 to 4 pounds
  • Increased fluid volume: 2 to 3 pounds
  • Fat stores: 6 to 8 pounds

Net total: 25-35 pounds

The main problem with that calculation is that there is no science showing the relative benefit of only putting on 6-8 pounds of body fat. As I’ve lamented in many previous posts, body fat is not a pathology; and in the case of pregnancy, it’s protective. There’s actually far greater of a health risk in not gaining enough weight during pregnant and/or not eating enough than there is to supposedly gaining or eating “too much.” Just like our bodies naturally maintain a genetically-determined body shape and size outside of pregnancy, they know how to gain the appropriate and healthy amount of weight that they need, at the appropriate time.

2. “You only need about 300 extra calories per day” is B.S.

Let’s suppose that a woman needs to gain that recommended 25 pounds as purely fat. This calculates out as follows: 25 lbs x 3,500 calories/lb of fat / 40 weeks of pregnancy / 7 days per week = 312 extra calories per day.

Now, keep in mind that for no pregnant woman is the entirety of her weight gain due entirely to body fat. Aside from the protective fat stores, there is a baby in there, as well as increased blood volume, growing organs (breasts and uterus) and the fact that an entirely additional organ is being created. On top of that, a woman needs to take in enough calories as building blocks to form that new tissue, and that tissue is also metabolically active. This means it’s not just in an anabolic state—converting energy (calories) into new tissue—but it’s also functional tissue. It uses energy to sustain itself. The baby itself, at term, burns through nearly 500 calories per day on its own. Taking in only an additional 300 calories each day in the third trimester would, more than likely, put a person in a calorie deficit which is extremely dangerous.

I also want to point out that the increased volume of blood and fluids isn’t purely water. Blood contains red blood cells (protein), hormones (made from cholesterol, AKA fat), albumin (protein), glucose (carbs) and all kinds of other necessary chemicals that need to be replaced as quickly as they are used up.

But let’s just say for a minute that the total amount of extra calories a pregnant woman needs throughout her pregnancy truly does amount to 87,500 (25 pounds x 3,500 calories per lb). It’s completely unreasonable to simply divide that number by the number of days of pregnancy because, as if it isn’t obvious, a wee, poppy-seed-sized fetus has very different nutritional and metabolic needs than a 38-week old baby, in utero. It’s reasonable that mom would need to eat less to feed baby in the early months, but that’s often when fat stores start growing. Why? Our bodies know that there’s an upper limit to how much we can eat. Store fat now, because most of our food will go to baby later.

3. Your Body Knows How to Grow a Baby

Women’s bodies have been growing and birthing healthy babies since the very first humans that walked on earth. They don’t need to be micromanaged, put in a box, or inflicted with rules. (That rarely works out well, anyways). Instead, they need to be listened to. They will tell us what they need, and more often than not, they’ll tell us something different than a nutrition textbook.

Just like your body knows how to self-regulate appetite and body weight when you aren’t pregnant, it knows how to manage those things for survival and thriving even when you are. So…relax, enjoy this special time, and take care of your body according to its needs.


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2 thoughts on “3 Reasons to Ignore the Calorie/Weight Guidelines for Pregnancy

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