Why You REALLY Need To Stop Undereating

By: Chris Huber

The Reason This Needs Discussed

I know most of us want a better body and we want it NOW. This leads to the common practice of trying to speed up the process of weight loss up as much as possible. The problem is that bigger isn’t always better. To drop body fat you need to create a caloric deficit, this can be done in a couple ways. One option is to work out more increasing your total burned calories for the day. The other is limiting your calories so you consume less overall. Both of these options work in your favor for the simple principle of weight loss (Calories In < Calories Out = Lower Body Fat Percentage) and I am a fan of a healthy mix of both, the issue is taking these options to the extreme.

Why You Stall Out

When I refer to a caloric deficit, I am talking about the difference between the calories you consume versus the total amount of calories burnt through the day (TDEE). If you would like to know more about how to find these values and what I consider a smart approach to looking at your diet, you can take a look at my previous post on Flexible Dieting (https://imfitcast.wordpress.com/2015/09/01/flexible-dieting/).

TDEE Chart

Now to the crux of the issue, after maintaining a large caloric deficit over a long period of time (months to years) your body will adjust in ways that are completely counterproductive your goals. Typically no more than a 500 daily deficit is recommended, with a 200-300 deficit for weight loss being preferred, but some take this to much greater extremes. You may not be familiar with the term adaptive thermogenisis (AT), but chances are you know the effects. As you can see in the figure above your BMR is the largest portion of your TDEE. Your metabolism is not a static number, it is better to think of it as a sliding scale. AT is your metabolism shifting in response to how much you eat. If you are at a large caloric deficit, your metabolism with literally slow down in response to being starved.  This process leads to weight loss plateauing because your total energy expenditures have now dropped.

To compound in addition to the issues of AT, your body has even more ways of sabotaging your weight loss if you practice extreme calorie restriction. Low calorie diets cause several hormones within the body to change. Leptin keeps you satiated and tells your body that your energy reserves are ready to be used. This hormone decreases when you diet hard, meaning you will become hungry and feel lethargic. Similarly the hormone ghrelin will increase which triggers your appetite to increase. Another problem hormone is cortisol. Cortisol triggers the breakdown of muscle mass while also increasing water retention. Add these effects together and you will notice weight loss stalling in a hurry.

Fixing The Problem

Recognizing you are taking a non-sustainable approach to fat loss is the biggest step. The longer you continue trying to lose body fat by severely under-eating, the worse the issues above become. You can go from weight loss plateauing to ending up with hormonal issues and no energy. To solution to these issues is fairly straight forward, you need to eat more. The application of this is a bit more complicated though.

I believe the best method to repairing your body is best outlined by Sohee Lee and Layne Norton in their method of reverse dieting. The basics of reverse dieting are slowly increasing your caloric intakes over an extended period of time. If you don’t already know a rough estimate of how many calories you current eat, I would suggest taking a week and eating normally, but tracking everything to find a baseline caloric level. From here you need to determine a calorie goal, which is going to be your maintenance level. You can find this easily using the Scooby calculator explained in the Flexible Dieting article. From here you are going to start at your current level of calories and begin adding 50-100 calories a week until you end up eating at maintenance.

This approach may be considered conservative to some, but I have my reasons. Firstly, you want to minimize the shock on your body. Jumping several hundred calories in one go will almost certainly cause weight gain, and no one wants to deal with that added stress on top of already trying to fix a frustrating situation. Secondly, trying to cram more food down your throat is tough for some people. You may genuinely not be hungry, even if you body is crying for those extra calories. Slowly building up allows your stomach to adjust to the added food.

My biggest piece of advice is to be patient. It took time to get to this point and it will take time to fix it. Try not to focus on the scale and do not expect to reverse the damage done immediately. You may gain a little weight here. You may feel like you will never achieve your goals. Just remember this is a bump in the road. You are becoming healthier and setting yourself up for success in the long run. You WILL get there in time.

Parting Thoughts

My goal here was to highlight a common issue in the fitness world. Too often you see low calorie diets marketed as the quick fix to all your problems. If I can make someone realize they are headed down a bad path, then this post was worth it. Sure, if you can maintain a caloric deficit you will certainly loose weight, even when starving yourself. The problem is the long term repercussions from doing this. Eat right the from the start or work now to fix the issue and you will end up in a much better place.


Trexler ET, Smith-Ryan AE, Norton LE. (2014). Metabolic adaptation to weight loss: implications for the athlete. Journal of the International Society of Sports Nutrition11, 7

Rosenbaum M, Leibel RL. (2010). Adaptive thermogenesis in humans. International Journal of Obesity34, S47-55

Lee, Sohee and Layne Norton. Reverse Dieting. Ebook