I touched on this concept briefly during the introduction of my book on page #9 of my Athletic Nutrition 101 book, which you can find more about here: http://www.athleticnutrition101.com/ and I wanted to take this opportunity to cover the topic in a bit more depth right now. There are a lot of factors at play when you sit back and analyze what happens when we restrict our body of energy as an athlete. There are two sides of the coin, with positive short term effects which have been shown through research, as well as less immediate and delayed outcomes coming later on that will more than likely result in setbacks and plateaus of athletic performance. For example, a study that was performed by a group of researchers back in 2015 monitored two groups who were prescribed lower calorie diets and then gauged their jumping and sprinting performance after four weeks. 1 To sum things up quickly, the group who consumed fewer calories with a 750 calorie deficit improved jump and speed markers better than the group who consumed more calories with a 300 calorie deficit. An argument that can falsely be made from this study is that fewer calories and weight are better. Not necessarily, unfortunately. Here are a few examples where this theory would not apply:
#1-A lightweight male or female with reduced energy needs
#2-A person with very little muscle mass
#3-Someone who has phenomenal maximal strength relative to their body weight
#4-A person with great single leg strength and natural transfer into power or speed based activities
If you take a male or female that weighs, say, 120 lbs. They will be expending roughly 2000 calories per day on days they train intensely for 1-2 hours. So if you reduce their calories by 750 calories, then they will be consuming right near their resting metabolic rate at 1200 calories. This can be approximated by taking someone’s bodyweight x 12. Of course, an actual RMR testing device would be more accurate, but this is a great ballpark that helps paint a picture. So in essence, this person is coming enough energy to maintain essential functions to stay alive. Examples include respiration rate, vision, temperature regulation, brain and liver functions, low-level muscle activity, keeping our heart pumping and any other function that requires low levels of energy. Also consider, this is only on days when they train hard. On other days they will be well below this number. The downfall is that it's well understood that our body naturally possesses a survival response that causes hormones, energy, and performance to crash if energy is cut too low for too long. As a general rule of thumb that threshold is around our RMR, which the study above clearly violates.
Another example is feeding someone who has very little muscle mass fewer calories. Aka a marathon runner. Are these guys ultra fast or ultra powerful? Not at all. They merely have tremendous aerobic capacities and a favorable body structure/weight to accommodate longer distances. Just take a look at the top performers in vertical jumps and sprinting. They are in a fed state which raises hormones that drive performance, and they have lots of muscle mass to generate more strength — thinking that lowering bodyweight so that you have less gravity and resistance to overcome is far too simplistic and automatically discounts the strength and power potential of muscles in the human body. If this were the case, the elite would be small, skinny, weak, and undernourished, but they are anything but when you examine their physiques.
If you can squat and deadlift 2-4 times your body weight, and you include a broad spectrum of speed and power based plyometrics in your program, then you are going to be able to easily overcome just your bodyweight when you go to sprint and jump and still apply a high level of the force you have earned and retained in the weight room. This is referred to as The Strength Reserve in sports science. The same thing goes for improved performance for single leg training, which is potentially better for some and more specific to sprinting.
So now we know from a physics and pure numbers standpoint that cutting calories and carrying “some” extra fat or weight isn’t as important as other training related factors in the grand scheme of things. But what would cause these performance boosts according to researchers if we aren't getting stronger or more powerful and our body hasn’t entered a starvation mode “yet?”
During the first Mesocycle (4 weeks) our bodies fight or flight response will kick in allowing us to perform better. Lyle Mcdonald, has noted that in the first week of dieting or calorie restriction the branch of our nervous system responsible for mobilizing energy increases by up to 5%. 2 This effect occurs in order to help send out hormones so that more energy can be removed by the body faster, and in turn we get greater fat burn, faster energy delivery, and potential neuromuscular benefits in the process. This slight boost will naturally elevate our muscular contractions and create temporary improvements that ultimately mask the downsides that will arise metabolically later on in the coming weeks as our body starts to slowly adapt to the reduced energy intake. This is one reason why the study I mentioned showed short-term performance increases. However, once this little honeymoon period is over, hormones responsible for detecting energy levels and food intake (i.e., Leptin) will begin to diminish and hunger hormones, fat storing enzymes (i.e., LPL), fat storing receptors (i.e., alpha type), and more will start to elevate to prepare for higher food consumption. This will result in weight rebound, which athletes or people trying to lose weight will hate, along with decreases in muscle building since this type of tissue is more disposable from a strict energy standpoint to a degree. Think about it for a moment. If we are depriving our body of energy and one of the main purposes of the human system is to conserve energy and protect us, wouldn’t it make more sense to let go of resources with less energy, like muscle, and fight to hold on and even increase tissues that contain more energy, like fat?
The main point is that as an athlete, don’t get caught up in all of the hype and restrict yourself of energy even if you do feel temporary increases in performance and a nervous system boost. It's a temporary effect that can hit you hard later on. You want to play the long game; otherwise, you will be swimming upstream for your entire training career against your own body, which is intricately and remarkably wired to protect and look out for you when you violate its design and threaten its precious energy stores. The smart approach is to reduce your calories slightly at maintenance levels, and research and real world evidence supports this strategy. In other words, you could multiply your current bodyweight by 12 and consume that number in calories per day to keep things humming along smoothly in the weight/fat loss department without taking a major hit in performance over the long-term!
#1-Huovinen, HT. Body composition and power performance improved after weight reduction in male athletes without hampering hormonal balance. J Strength Cond Res, 29 (1): 29-36, 2015.
#2-. McDonald, Lyle. The Stubborn Fat Solution. Lyle McDonald Publishing. 2008. SCRIBD. Web. https://www.scribd.com/document/337430424/Lyle-McDonald-The-Stubborn-Fat-Solution-pdf