Welcome to Part One of our two-part series highlighting the ways in which undereating may lead to slower fat loss for your clients. The first part focuses on how undereating slows progress so you can understand it as a coach. Part two will focus on tangible strategies that you can utilize to help your clients navigate these issues. We will start with a broad perspective and get into the specifics down the road.

It’s human nature to want to simplify things. This holds true when we think about nutrition. Oftentimes, in nutrition circles, you hear the old adage “calories in versus calories out.” While there is merit to this statement, helping your client change their body composition requires more than just scratching the surface. 

Accepting such a statement as gospel has its perils when working with clients. They may have been taught that simply eating less than they burn will suddenly make them look like a mix between Michael Phelps, Dwayne Johnson, and Jennifer Lopez. As a coach, it’s your job to teach them that there may be more to the story. 

However, the human body is like a high school algebra equation. It wants to be balanced. It pulls out every stop in the mathematical textbook in order to do so. It carries the two, it divides by pi, it multiplies itself by an imaginary number. As I said, it’s perilous.

One of the most common misconceptions that I run into as a nutrition coach is that as long as you eat less, your body will lose weight. Although true for some, this is not true for all.

Many people with goals of losing fat fail to understand the effect of manipulating “calories in” with “calories out.” 

It’s not their fault—it’s what the media has been telling them since they first decided to “lose weight,” and they came to you for a reason—for guidance. Sometimes, this guidance may look very different than what they originally thought they were signing up for. As WAG coaches, we often hear our clients say, “I had no idea I could lose weight without being miserable and hungry” or “I didn’t know I could eat this much and still reach my goals” or “I’m eating more now than I ever have before!” This is music to our ears. 

The body is smart. It knows when it is being underfed. It still thinks it’s in prehistoric times and an underfed body doesn’t bode well when you’re being chased by a saber-toothed tiger. The body compensates. It downregulates metabolism, spends less energy on “background processes” (like digestion, reproductive, general hormone health, and more).

Then, sure enough, a client is eating less and the scale, mirror, or measurements don’t change. They may grow frustrated and give up altogether, and as a coach, you may start thinking, “I have nowhere to go here, they can’t eat less than this.” 

I’m going to let you in on a secret. The body needs to feel “safe” to safely, healthily, and efficiently lose weight. The question then becomes, “How do we maintain a caloric deficit while keeping our clients’ bodies in a low-stress state so they feel “comfortable” tapping into stored energy (aka body fat)? 

As coaches, we achieve this by setting client deficits that are appropriate for these conditions to support metabolism so it revs on all cylinders and promotes better baseline fat burning. This ensures that our clients eat enough to keep the fat-burning process strong without eating too much and beginning to store fat! It’s a fine line and balance.


You read that correctly. Oftentimes, our clients need to eat MORE “calories in” to lose weight.


I like to think back to my favorite fairytale: Goldilocks and the Three Bears. The chairs, the porridge, and the beds need to be JUST RIGHT. Caloric and macro goals need to be the same—just right. There’s a reason we give clients a macro prescription and not a macro maximum. It ensures that they eat enough. 

This is a topic that would best be served by an example. Are you ready for some math?

Jill is an individual with a resting metabolic rate of 1,300 calories. A resting metabolic rate is the calories required to keep you alive, combined with the calories needed to support your non-training activity throughout the day. This is the energy required to walk to the bus, to perform your job, and to take care of your family. You can influence it in one way or another by taking the stairs, walking to work, or even playing with your dog a bit more. Jill also burns 400 calories through exercise on most days, which puts her “calories out” at 1,700. She is looking to drop body fat so her nutrition coach has set her calories at 1,500 each day. 

But Jill is an overachiever—she’s been that way since first-grade art class when her teacher put an “Excellent” sticker on her self-portrait. She thinks, “I’ll show them. I’m only going to consume 1,300 calories per day and double my deficit, which is sure to also double my rate of progress.” Jill loses no weight over the course of her first month and it isn’t until her coach shows her this article that she goes back to consuming 1,500 calories. 

Here’s what happened:

  1. Jill’s body went into a panic and by only consuming 1,300 calories per day, her resting metabolic rate dropped to 900 calories per day, which was dangerously low for someone her size.
  2. Her resting metabolic rate (RMR) of 900 calories and her 400-calorie burn, which really turns into 300 because she has no energy for training sessions, puts her at 1,200 calories.
  3. She’s only eating at maintenance because her RMR regulated because her calories were just too low.
  4. She also may be taking extra bites because she is so hungry, and not sleeping well, which impacts hormone regulation and water retention, and so she is SUPER frustrated with her progress.
  5. Once she gets back to consuming the PRESCRIBED macros and calories, her metabolism revs up, she is able to push harder in training and she finally creates that 200 calorie per day deficit.
  6. She loses fat and starts noticing differences on the scale and in her progress pictures.

There you have it! While calories in versus calories out is a principle in body composition manipulation, it’s not as simple as it seems. The body wants to balance that equation and will alter a client’s metabolism to do so. Undereating could lead them just as far from their goals as overeating. The trick is to decrease calories enough to burn fat without sending the body into a metabolic panic.

Now that you have a great, theoretical understanding of how undereating can limit client progress, be sure to stay tuned for Part Two! We’re diving into specific strategies that you can make actionable for clients, to improve their buy-in and ultimately improve their results! We will also touch on what you should expect as a coach so you can predict and quell the worries your client may have.