Undereating vs Overeating and Weight Loss

How many times have you heard the above phrase or have even said it yourself?

It seems logical though- to achieve weight loss, you have to eat less. However, this is not always the case. Many people are actually stalling their weight loss due to UNDEREATING and not OVEREATING.

To understand this phenomenon, we must talk about metabolism and its five components.

Each person has a metabolism. Your metabolism is the combination of all the processes going on in your body all the time. The foods you eat are going to fuel the buildup and breakdown of nutrients in your body that are necessary for optimal health. Ultimately, your body needs adequate energy intake to stay active, support day-to-day activity, maintain (or grow!) muscle, and keep you from experiencing fat gain or weight plateaus. However, undereating can greatly impact your metabolism in a negative way and affect the five components of metabolism.

Basal Metabolic Rate (BMR) and Resting Metabolic Rate (RMR)

Your BMR is the minimum energy needed to keep vital bodily functions fueled (your heart rate and being able to breathe). This accounts for about 70% of the total energy you expend each day. Your RMR is similar to BMR in that it is measuring minimal bodily functions however, RMR covers respiration, circulation, creation of organic compounds (think building muscle), and primary cellular functioning. Furthermore, your RMR is 60% of your total energy expenditure.

How undereating affects BMR and RMR — BMR and RMR are affected by body size, composition, age, gender, climate, and hormones. People with more lean body mass have an RMR that is about 5% higher than people with lower muscle mass. If you’re not eating enough to fuel your muscles, your RMR will be lower and you will burn fewer calories at rest. Coincidentally, undereating can also cause hormone imbalances. This can cause water retention and unwanted fat storage.

Thermic effect of food (TEF)

This is the energy expended in the digestion, breakdown, and absorption of the foods you consume.

How undereating affects TEF — Eating food takes energy. Chewing, swallowing, digesting, creating the enzymes that break down your food — all these functions cost you calories. Protein especially has a high thermic effect, which means it takes your body extra energy to digest, process and store protein. On the other hand, fat has the slowest thermic effect. But when we undereat, we are decreasing this overall calorie output and more importantly, this is why you must make sure that you're eating sufficient protein to support your muscles and support the breakdown of protein.

Exercise activity (EA)

Your exercise activity includes intentional exercise (think going for a run or hitting a CrossFit class). EA can vary drastically from one person to another, accounting for anywhere between 10% (or less) to 30% (or more) of total daily energy expenditure.

How undereating affects EA — Have you ever had a day in the gym when your energy was through the roof and you felt like you could go forever? Or have you ever had a day when you were dragging and felt like you didn’t have enough energy to do the things you wanted? Making sure that you're consuming adequate calories to support exercise allows you to push hard in the gym, build and maintain muscle and get stronger. Sufficient nutrients also support quick recovery so you can hit it hard again the following day.

Non-exercise activity thermogenesis (NEAT)

This is the most variable part of energy expenditure from person to person. It includes all energy expended for the activities you do that don't involve eating, sleeping, breathing or exercising. NEAT includes things like doing yard work, standing instead of sitting at work, fidgeting, walking around the grocery store, meal prepping, taking your dog for a walk, etc. A prime comparison would be the NEAT of a construction worker versus the NEAT of a person who works at a desk. Due to the high demand that being a construction worker has on the body, their NEAT could be 2,000 higher than the business person.

How undereating affects NEAT — When you are under-fueled, your body will automatically start suppressing your NEAT to conserve energy. This means you will naturally start moving around less, opt for the closest parking spot, avoid taking your dog for a walk, and sit instead of stand at your desk, etc.

Again, we get it- the idea of "eating more to lose weight" seems absurd. Nonetheless, you do have to ensure that you're consuming enough calories to support your metabolism and your lean body mass.

If you're interested in learning more, shoot us a message on our website or on our FaceBook page at CrossFit-235.

-Coach Karina, BS-Kinesiology, CF L1 Trainer, USAW Sports Performance Coach