Why You’re Tired, Craving Sugar, and Plateauing: Underfueling Explained
If you’re tired, unfocused, craving sugar by mid-afternoon, or feeling flat during workouts, there’s a good chance your problem isn’t discipline — it’s underfueling.
High performers burn more energy than they think. And most of them aren’t eating nearly enough to support the pace they’re trying to maintain.
One of the sneakiest ways I see many of my clients run into roadblocks with their progress boils down to a matter of underfueling, which can eating too little, fueling incorrectly, or not balancing fuel for the demands put on the body - or for a combination of all three. In many cases these aren't conscious decisions being made, or they're decisions that seem correct but lack context, and as such correcting them can be challenging. It takes a little more digging to not only identify the issue but also recognize how simple the solution might be.
Underfueling is one of those concepts that sounds simple and yet in practice is complicated enough that it goes unnoticed. The main idea is that you're not providing enough quality fuel for you body to perform the tasks that you're asking it to. The body is also very good at adapting and compensating for these deficiencies, but can only do so for a period of time before it becomes overwhelmed. A couple of the main culprits are caffeine and fiber as while they are beneficial in many ways, they also will dull or mask hunger queues such that skipping meals entirely or not fueling enough becomes not only easy but can become consistent. The first part of the challenge is underestimating the caloric needs of the body, some like basic daily needs (Basal Metabolic Rate or BMR) and training load are relatively straightforward to get a good estimate as there are calculators and wearables to help. However, these can also be wildly inaccurate, especially when estimating caloric needs based on exercise. In addition, other factors such as poor sleep, mental stress load, travel, and injuries will all skew your fueling needs and not always in magnitudes or directions as you might expect. Based on all these factors, it can be hard to get a handle on the caloric needs and even being off a couple hundred calories a day can create a sizeable enough gap to cause challenges.
So what does underfueling look like, or what are some of the symptoms you might notice? First off, physically you may notice:
Low energy or consistent fatigue
Inability to concentrate or brain fog
Frequent illness
Poor sleep
The symptoms don't stop there, you will also notice struggles mentally as well:
Irritability or mood swings
Decreased libido
CRAVINGS
night time snacking
And then to further compound all of this, you'll notice some performance and metrics dip as well:
Workouts feeling harder than normal
Heart rate variability (HRV) dips
Higher than normal resting heart rate
With all of this, it may seem daunting to overcome this challenge - however, the first step is quite simple, remember simple doesn't always mean easy. I've mentioned this before, and will continue to suggest it - but awareness is your greatest asset for this kind of situation. And that comes down to:
Understanding your body's needs including not just calories but the allocation of those calories between carbohydrates, protein, and fat.
A good handle on your intake and timing of your fueling including the macro breakdown.
A honest self assessment of how you feel on a daily basis such that you can better understand where you may be lacking.
Another option you could consider, if you feel like you're experiencing a number of the symptoms, would be to increase your caloric intake by 200 to 500 calories, paying attention to how you feel. This could come from the addition of a snack, or if there's a particular meal (like breakfast) you typically skip, add that back in. Do this for a week or so, and see if you notice any differences. This is also a time when using a scale can be helpful to notice if you're gaining any weight, but with the increases I'm suggesting it would probably take a couple of weeks before you noticed anything significant considering the normal day to day weight fluctuations. Continue to balance how you feel with the numbers you're seeing on the scale and look to continue to increase the calories without seeing a consistent weight increase. I typically recommend increasing for a couple of weeks, then taking a week to hold steady to help accurately assess the dynamics.
Travel, busy seasons, and packed schedules make underfueling even more common. But they don’t have to derail your performance.
Learn how to fuel consistently no matter where life takes you — and build the foundation that drives your energy all year long.
🔗 Subscribe to The Wellness Forge for more tools to support strength, energy, and recovery.
