Hormones, Calories, and Weight Gain

By Igor Klibanov

Many women going through menopause wonder, “Why am I gaining body fat if I’m eating the same, and exercising?” They conclude, “It must be my hormones.” And, they are (largely) correct. But how do hormones really affect body fat? Do they slow down metabolism? Do they stimulate appetite? Is there another mechanism? And, likewise, how does food influence hormones?

Yes, hormones affect calories, but the opposite is true as well – calories affect hormones. In this article, we’ll explore the intricate relationship between hormones and calories.

We’ll answer questions like:

  • What are the four ways in which calories are burned?
  • How does estrogen affect calories?
  • How does thyroid affect calories?
  • How do calories affect hormones?

What this article will not cover is how to balance hormones. I’ve written an entire book on that, called STOP EXERCISING! The Way You Are Doing it Now. If you would like to download a free PDF version of the book, you can do so here.

How Are Calories Burned?

When we talk about having a “slow metabolism” or a “fast metabolism”, what does that really mean? Often, we use it as an excuse as to why we have a few extra pounds (it’s easier to blame our metabolism – something seemingly outside of our control, rather than something like what we eat, which is within our control). Too bad this excuse isn’t valid at all, since overweight people have faster metabolisms than normal weight people (after all, a person who weighs 200 pounds burns more calories than a person who weighs 150 pounds).

But, when we (the laypeople) say “metabolism”, we’re referring to how many calories we burn per day. Though to be technically accurate, that’s only one of four sources of caloric expenditure.

There are four ways that calories are burned, and all combined they’re called the “Total Daily Energy Expenditure” (TDEE for short). They are:

  • Basal metabolic rate (BMR): How many calories you burn just to stay alive. This contributes around 40-50% of your total daily calories. So, if it takes you 2000 calories per day to maintain your weight, you spend about 800-1000 calories on BMR.
  • Exercise. This one’s obvious. Depending on how much exercise you do, that will determine how many calories you burn.
  • Thermic effect of food (TEF): Whenever you eat food, you don’t absorb 100% of the calories. Some of those calories are used to help with digestion and assimilation of food. TEF is estimated to be about 10% of daily calories. So, if you need 2000 calories to stay the same weight, TEF will be around 200 calories.
  • Non-exercise activity thermogenesis (NEAT): These are movements and activities that aren’t formal exercise, but they burn calories. Things like gardening, taking the stairs instead of the elevator, fidgeting, etc. NEAT is a real “wild card” when it comes to metabolism and a lot of people believe that NEAT makes the difference between those who are naturally lean and those struggling with their weight. NEAT can range from as little as 100 calories to over 1000 calories per day (things like treadmill desks can really boost your NEAT without making you tired, since the intensity is so low, but spread out over eight or more working hours).

How Does Estrogen Affect Calories?

We know from the previous section that we can burn calories through BMR, TEF, NEAT, and exercise. So, which of those four does estrogen affect, and by how much?

That’s what this study wanted to find out. Here’s what the researchers did:

They recruited 45 women, and divided them into two groups:

  • Group 1 received a placebo (they were told they were receiving estrogen, but in reality the cream they received had nothing in it).
  • Group 2 received estrogen therapy

Both groups received the treatment for five months and here’s what happened afterwards:

  • BMR:
    • In group 1, it dropped by an average of 54 calories per day.
    • In group 2, it went up about six calories per day.
  • The amount of calories burned through exercise:
    • In group 1, decreased by about 8%.
    • In group 2, it decreased by about 5.5%.
  • TEF increased by a similar amount in both groups (about 10-12%)
  • NEAT:
    • In group 1, increased by about 19 calories per day
    • In group 2, increased by about 41 calories per day.

If you’re an accountant, engineer, or scientist, you probably love all these numbers. If you’re not, you’re probably just glazing over and wondering what the implications of these results are. Here it is:

  • Women with higher estrogen levels during menopause burn more calories at rest, they burn more during exercise compared to women of equal age, but with lower estrogen levels, and they are slightly more active during the day.

All in all, it adds up to less fat and more muscle.

So, you must be wondering how you can raise your estrogen levels so that you too can have less fat and more muscle. Unfortunately, it’s not quite as simple as getting started on hormone replacement therapy.

You have to ask yourself why estrogen levels are low to begin with. For any one issue, there are multiple potential causes. Here are some potential reasons why estrogen may be low:

  • Testosterone is low (estrogen is made from testosterone so, if you have low testosterone, that may be causing low estrogen levels)
  • Cortisol (the stress hormone) is high
  • The liver isn’t processing estrogen effectively
  • The gastrointestinal system isn’t working properly
  • …and others

So, it’s a fairly lengthy process to figure out what’s going on and the most appropriate course of action is to see a medical professional for hormonal testing and interpretation.

Besides the involuntary aspects (metabolism, thermic effect, and NEAT) of having higher estrogen levels, one study found that women with higher estrogen levels naturally want to exercise more and harder.

And another study found that women with higher estrogen levels get more pleasure and satisfaction from their food, so they don’t feel the need to eat as much.

In summary, how do low estrogen levels cause fat gain? Through a quadruple whammy of:

  1. Burning fewer calories at rest.
  2. Doing less involuntary physical movement.
  3. Doing less exercise, and less intensely.
  4. Eating more because food isn’t as satisfying as it was when estrogen levels were higher.

How Does Thyroid Affect Calories?

Often, in women going through menopause, it’s not just one hormone that’s “out of whack” – it’s a whole bunch of them: estrogen, progesterone, cortisol, and thyroid.

We covered estrogen in the previous section. In this one, we’ll cover thyroid (the reason we don’t cover progesterone and cortisol in this article is because very little evidence exists on how they impact TDEE).

The thyroid is a butterfly-shaped gland that sits in the middle of your throat and it’s the “gas pedal” for your metabolism.

As much as two thirds of BMR is used just to keep you warm. In other words, it’s used to maintain your body temperature at healthy 36.5-36.8 degrees Celsius. So, if your temperature is lower, you’re burning fewer calories. And one of the most common symptoms of a slow thyroid is low body temperature. People with a slow thyroid often complain that their hands and feet are cold all the time, even when other people around them are comfortable. Or they’ll often sleep with socks on.

For every degree Celsius that your temperature is under that 36.5-36.8 range, you’re burning 10-13% fewer calories, according to this study. In one client, I measured her temperature at 34.2. Therefore she was burning about 25% fewer calories than she thought she was.

One study decided to look at how many calories are burned by people with hypothyroidism. People without hypothyroidism had a BMR of 1591 calories/day while people with hypothyroidism had a BMR of 1316 calories per day – a difference of 275 calories. With that kind of deficit, that’s equal to gaining a pound of fat every 13 or so days. However, when thyroid hormone was given to people who had a slow thyroid, their metabolism increased to 1623 calories/day.

Of course, just like there are multiple reasons for low estrogen, there are also multiple reasons for a slow thyroid:

  • High cortisol
  • High estrogen
  • The immune system is attacking the thyroid gland
  • The body is resistant to thyroid hormone
  • High levels of mercury
  • …and others

How Do Calories Affect Hormones?

We’ve covered how hormones affect calories, now let’s switch gears and talk about how calories affect hormones.

First of all, not all calories were created equal. Calories are divided into three different categories and each one has a different hormonal effect:

  • Carbohydrates (found in sources like bread, pasta, rice, potatoes, beans, lentils, peas, etc.)
  • Fats (found in sources like butter, olive oil, nuts, avocados, fatty fish like salmon, etc.)
  • Protein (found primarily in sources like meat, fish, and seafood. You can read my article on the best protein sources).

Carbohydrates and Hormones

The most obvious effect of carbs is on insulin. When you eat carbs, blood sugar rises. When blood sugar rises, insulin also rises in order to bring blood sugar down. Usually, blood sugar overshoots the baseline, goes a bit too low, and so cortisol is released, to bring it back up to baseline. So, there’s this teeter-totter between insulin and cortisol. Insulin lowers blood sugar, and cortisol raises it.

What is not as well known is the effect of carbs on your thyroid. According to multiple studies (here’s one of them), it appears that low carbohydrate diets slow down the thyroid. However, once normal carb intake is resumed, so is thyroid function.

Fats and Hormones

Dietary fats influence a hormone called “leptin.” Leptin is the hormone that tells you that you’re full. It’s the “satiety hormone.”

What is not as well known about fats is that they can actually increase testosterone levels in both men and women. People who are on low fat diets have lower levels of estrogen, progesterone, and testosterone. That is because all three are made of cholesterol. If cholesterol is too low, typically so are all three hormones. However, if all three hormones are within normal range, it doesn’t seem likely that additional dietary fat will increase them.

As I’ve written about previously in my article on PCOS, women with this condition seem to actually do better on a higher fat diet (where it makes up about 30% of daily calories), compared to lower fat diets.

Protein and Hormones

Like carbohydrates, protein can also raise insulin levels, but not nearly to the same extent.

Sufficient protein intake (1.2-2.0 g/kg/day) keeps testosterone levels where they need to be, but low protein intake can actually decrease testosterone levels.

So, why am I gaining body fat if I’m eating the same and exercising?

So, by now, it should be making sense why you might be gaining body fat, even when no other changes were made.

Imagine this scenario: it takes you 2000 calories per day to maintain your weight. So, you eat 2000 calories per day and through a combination of exercise, metabolism, TEF and NEAT, you burn 2000 calories per day. Your body fat is stable.

Then comes peri-menopause, and both your thyroid and estrogen decrease. You’re still eating 2000 calories per day, but your BMR is now 100 calories per day slower and you don’t move around as much involuntarily, so you burn another 100 calories per day less. Now you’re burning 200 calories per day less than you were just a few years earlier, before your hormones started to change.

You’re taking in 2000 (that hasn’t changed). You’re still exercising and eating the same amount (that hasn’t changed either), but you’re not burning as much. It doesn’t take a math genius to figure out that if you take in more than you expend, you’ll gain body fat.

And that’s often the complaint with our menopausal clients.

This is the challenge. Although, we don’t talk about the “what to do”, I do cover that in my book, STOP EXERCISING! The Way You Are Doing it Now. If you want to download a free digital copy, you can do so here.


Igor Klibanov is the author of five books on fitness and nutrition, as well as the CEO of one of Toronto’s premier personal training companies, Fitness Solutions Plus. He was selected as one of the top five personal trainers in Toronto by the Metro News newspaper, and has performed approximately 400 speaking engagements, many of which have been to some of Canada’s largest corporations (including RBC, IBM, Intact Insurance, and others).

Additionally, he has multiple programs for personal trainers to enhance their skills and is a regular speaker at various personal training conferences, including canfitpro.