My years as a college instructor, the topic of how our body utilizes food for energy is always a hot topic of discussion. Do I eat carbohydrates, no carbs, eat fat, no fat? I will first boil things down as to what you should be eating, and it all depends on your energy expenditure. Simply, what are you doing in the course of a day? Are you sedentary? Active? What type of activity do you engage in? If you are like many 40-something year old, you might be more than likely sedentary. This being the case, it is crucial that you minimize your carbohydrate intake, so sticking with mostly fruits and vegetables with the occasional whole sprouted grain should provide you adequate calories to meet your demands. “I will be hungry!” No, you won’t. This is why you need to add in some good fats to help your energy levels, such as avocados, cooking with olive oil or coconut oil, and some nuts and seeds. This will provide your body slow burning energy, and not allowing your blood sugar levels to rise and create hunger sensations.
Now, if you do hit the gym, it is important that your body has a quicker energy source to burn for fuel, this might be were you can add in more of the whole sprouted grains (Quinoa, buckwheat, brown rice) and sweet potatoes are a great energy source. But remember, if you plan to burn about 300 calories, there is no need to overload the carbohydrates if your goal is ultimately body fat reduction.
Here is my research on why, what and when it is important to consume your calories:
In a study by Kerksick (2008), research showed that ingesting high amounts of carbohydrates prior to a high intensity exercise session helped maintain glucose levels in comparison to subjects who were on low carbohydrate diets prior to the event, providing evidence that prolonged performance can be sustained for a greater time frame when ingesting more carbohydrates prior to the event. During exercise, maintaining blood glucose levels are critical for continued high output performance. In a similar study reported by Berksick, cyclist who ingested liquid carbohydrate at the onset, and during the event, maintained high blood glucose levels providing longer output to reach exhaustion. The key component to the study was glycogen levels at the onset of the activity. Those that had low glycogen levels prior to training were able to benefit from the ingestion of carbohydrates during activity. Subjects with high glycogen levels at the onset did not see much improvement from ingesting liquid carbohydrates during exercise. Relating these studies to my personal plan, ingesting of carbohydrates at least an hour prior to the session is important in maintaining proper glucose levels. I personally do not like to enter in to a fitness session with a full stomach, so I typically prefer to ingest fruit and nuts as a means to increase glycogen stores. I rarely find that during my style of workout, that I have little energy left to complete my session, so the idea of ingesting carbohydrates during my workout has not been a factor. I would plan to do so if the workouts became longer than 1 hour in duration with a similar intensity level. In regards to carbohydrate consumption, foods that rank low on the glycemic index are important to not raise insulin levels too quickly and aid the body in the production of fat. In the NSCA Performance Training Journal (Vol 2, #5), insulin helps promote fat production from the glucose in the liver and adipose tissue, and blocks the fat release from fat cells. So foods that are low on the glycemic index I would typically consume prior to a workout would be fresh fruits and vegetables, and some nuts and seeds to provide some additional protein and fat.
Low carbohydrate diets for an active individual would be counterproductive to their efforts of peak performance. Our body requires a constant energy supply, so depending on the intensity level and time frame of the activity would best determine the type and amount of carbohydrates to consume. It would be a basic explanation of Bioenergetics to understand how and why the muscles contract and for how long. The body requires ATP in order for a muscle to contract. This ATP is stored in limited amounts in the muscle and can typically sustain muscle contraction for approximately 6-10 seconds. Once that is depleted, the next available source to convert to ATP would be glycogen that is stored in the muscles and the liver. During moderate to high intensity exercise, carbohydrates (in the form of glycogen) supply more than 50% of the energy stores to the body (Cermack, 2013). Low carbohydrate diets would minimize the body’s ability to convert additional ATP and fatigue would typically set in with inadequate stores. With adequate amounts of glycogen, this glycolysis phase can help sustain muscle contraction for a couple minutes. After that, the body requires the presence of oxygen to help convert the pyruvic acid to the mitochondria to enter the Krebs cycle, which allows for a longer supply of ATP. Without adequate stores of glycogen in the muscle or liver, muscular fatigue will occur prior to the aerobic glycolysis phase which will mean a decrease in overall performance.
Kerksick, C., Harvey, T., Stout, J., Campbell, B., Wilborn, C., Kreider, R., & … Antonio, J. (2008). International Society of Sports Nutrition position stand: nutrient timing. Journal Of The International Society Of Sports Nutrition, 517. doi:10.1186/1550-2783-5-17
Cermak, N., & Loon, L. (2013). The Use of Carbohydrates During Exercise as an Ergogenic Aid. Sports Medicine, 43(11), 1139-1155
D’Assisi, Anthony, BPHC, CSCS, NSCA Performance Training Journal, Volume 2, Number 5, October 2003. The Reinvention of Nutrition Basics.
American College of Sports Medicine, Nutrition and Athletic Performance, 2009.