Hierarchy of energy sources

My background, prior to the pacemaker world, is in Genetics. For those of you who don't know (because I didn't when I signed up to major in the subject at A&M), Genetics is not the study of rare, provocotive diseases. Well, you study them some times. The majority of my coursework was math, biochemistry, biology, microbiology, chemistry, biochemistry, chemistry ... You get the idea. I spent many nights wondering what I got myself into and why I hadn't chosen an easier major.

Chemistry was never my subject. In fact, my first C ever was in my second semester of Organic Chemistry (evil class). However, biochemistry, while still difficult, was fascinating to me. It's probably the most self-centered characteristic to desire to learn exactly how processes work in the body because you want to know how your body operates. It's also the most rewarding, and I still draw on my biochemistry knowledge when interacting with my patients today.

One area I've always been drawn to (for obvious reasons) is the biochemistry of dieting and weight loss. When I was at A&M, the Adkins diet was all the rage. And then when I was in grad school, whole grains really started to gather steam as a healthy alternative to traditional pastas and breads.

I still have a lot to learn about how you burn calories when you work out. There seems to be a great deal of information about this subject, however, a lot of it is in disagreement. I can't seem to find a good source of information on the internet that says "this is how calories are burned, and this is the breakdown of those calories, and this is the graph of heart rate to calories...". I'm sure this information is available in text books, but come on. Who pays for information any more?

Last weekend they were having a sale on sport watches and telemetry bands at my gym so I bought one. It's pretty cool. It gives me my heart rate, and breakdown of time in each heart rate zone, calories burned, and the percentage of those calories that come from fat.

Interestingly, when I run or take a spinning class, my heart rate goes really high, >170 bpm. I've always thought this was a good thing - I'm not chronotropically incompetent. However, I noticed that after these workouts, my percentage of calories from fat is very low - 13-17%. I understand this is an estimate from a watch but I don't think it's too far off. On the other side, when I do low-impact work outs or circuit training, my heart rate only gets up to about 155 bpm, but my calories from fat percentage is much higher, 25-35%. This is because there is a hierarchy of energy sources in the human body.

The way your body uses fuel (carbs, fats, protein) is based on many different factors, such as gender, hormones, underlying medical conditions such as diabetes, etc. I'm just speaking in generalities today. Most humans burn energy in the following way - carbohydrates first, then fat, then protein.*

Using protein for fuel is a biochemically complicated and energy inefficient process. That's why you don't usually see people who are breaking down proteins in their bodies for energy unless they have severe illnesses such as anorexia.

Carbohydrates are the easiest for your body to break down and the go-to energy source for hard-core athletes. This is because you burn a TON of carbs when your heart rate is high and you're exerting yourself to the max.

Your body burns fat while you sleep, when you're going through your day, and when you work out. The way your body uses fat is interesting. It uses your fat stores and turns them first into sugar, and then into energy. Fat is a great energy source, providing 9 calories per gram. Carbs and protein provide 4 calories per gram.

Tired of the biochemistry yet?

The reason why all of this is important is that if you are trying to reduce your body fat, you can maximize your time at the gym by doing low-impact workouts that keep your heart rate in the fat-burning zone. And the great news? These workouts are perfect for beginners!

As for diet, eating a high protein, moderate carb, low-fat diet is going to maximize your weight loss. Why? Because your body won't use the protein you're ingesting. It will use the carbs you take in and the fat stores already there to provide energy to your body. A diet high in fruits, vegetables, and fiber also contributes to weight loss by regulating your digestive system.

A bit verbose entry, I know. But it's essential to understand how your specific biochemistry functions to maximize your results.

Weight loss this week ... not so good. I'm at 138.1 lbs.

So, a gain of 0.1 lbs. Looking forward to next week.

*Disclaimer: I'm not a nutritionist, and I'm drawing on knowledge that is ~7 years old. Please forgive any inaccuracies.