Fat for Fuel

Photo: The ultimate fat burn—nine days, eighty miles off-trail alpine hiking. Bonneville Pass with Pronghorn Peak, Wind River Range, Wyoming 2017.

Slipping off my pack, I slumped to the alpine tundra back resting against a granite boulder… exhausted. It was late afternoon, the sun tracking low in the sky above the mountain ridge to the west. It was August 20^th, 2017, four days into an eighty mile solo through-hike named the Wind River High Route along the spine of the Wind River Range Mountains in Wyoming. Earlier that day I crossed snow covered Indian and Alpine passes, traversed Upper Alpine lake surrounded by giant boulders and climbed a short, but difficult rock wall with a full pack; ten hours of hard off-trail hiking. Tomorrow, deep in the wilderness above timberline, I would be treated to a total eclipse of the sun, but right now I was dealing with reality.

I was behind schedule. Turning back was not an option—my car parked fifty miles to the south. I packed food for eight days; 1900 calories per day. With four days left, adding another day required cutting rations by twenty five percent. With estimated energy expenditures at 3800 calories per day, I planned on burning fat reserves for fifty percent of my daily energy requirements. Could I do over sixty percent?

The average adult has between 1300 and 1500 calories of carbohydrates stored in the body as glycogen in muscles and liver; and as blood glucose. We can perform a moderately intense workout for 2 to 3 hours using these stored carbohydrates without consuming extra carbs during a workout. Compare that to the average fat storage of 80,000 calories. At rest, a body burns 50% to 80% fat. As the intensity of your exercise increases, the body’s ability to burn fat diminishes. This is because the high demand for energy in the muscle favors carbohydrate oxidation and inhibits fatty acid oxidation.  At our anaerobic threshold, approximately 75 to 90% of maximum heart rate, we are burning 100% carbs. Can you train your body to burn more fat as fuel? Can you increase your anaerobic threshold? Yes to both.

Benefits of Improving your Fat Burning Efficiency

You can teach your body to be an efficient fat burner through exercise and diet. Doing so improves your health, helps lose weight, lowers body fat, and improves athletic performance. If you are active, recreationally or professionally competitive, you want optimal health to achieve your goals. By improving your body’s ability to burn fat you will:

1. Burn more fat as fuel
2. Improve your fasting insulin levels
3. Feel more satiated
4. Improve your concentration and focus
5. Lower your carbohydrate needs during exercise
6. Reduce gastro-intestinal issues
7. Reduce moods swings associated with insulin spikes
8. Sustain longer periods of exertion without the need for additional calories
9. Decrease your risk of “lifestyle disease”
10. Improve your sleep

Over the years, many of my clients were poor fat burners. Some had a good diet, but lacked the proper exercise routines. Others were competitive athletes, but had the wrong diet. Each situation is unique. There is no magic bullet.

Nutrition Strategies for Fat Burn Improvement

If over half your diet is carbs, chances are you a poor fat burner with resting fat burn of 50 to 60%. You burn what you eat. You have taught your body to burn sugar and preserve fat. By shifting your diet towards more protein and healthy fats you can improve your fat burn percentage. My basic metabolism (not including exercise or hard work) is 1800 calories per day, I try to keep my carb intake around 600 calories. Read the labels. That is no easy thing. But it works. I have trained my body to burn 80% fat at rest and 60% at moderate exercise.

I had a client who was a strong cyclist, but she complained about bonking (a sudden drop in power output) on hard bike rides. Her diet was healthy, but low in protein and healthy fat. She was a sugar burner. Changing her diet over time eliminated the bonk.

For more information on getting lean see my blog Get Lean and Stay Lean.

Training Strategies for Fat Burn Improvement

I train myself and my clients to improve our fat burn through interval training. I use a combination of strength and aerobic training; sometimes in isolation, other times in combination. Your goal is to adapt your body over time. The stronger our cardiovascular system, the greater our VO2 max which is the best predictor of cardiovascular health. The higher our VO2 max, the more efficient our muscle become in using fatty acids for fuel rather glycogen. For more on interval training see my blog Interval Training

To improve our body’s ability to burn fat, I train with intervals in my client’s maximum fat burning zone. This generally at 50 to 65% of your maximum heart rate. Over time, I push those intervals longer and at higher intensities. The body adapt and your fat burning efficiency rises. To push out our anaerobic threshold, I train my client to do intervals at 75 to 85% of their maximum heart rate. Over time the body adapts as we push the intervals harder and longer. My anaerobic threshold is 92% of my maximum heart rate.

A client of mine had a goal to climb the Grand Teton in Wyoming. See my blog Gary’s Big Day. Over six months of training he lost fifteen pounds, lowered his body fat percentage, increased his strength, improved his VO2 max and gained endurance. At 60 years old he summited the Grand last summer.

The Ultimate Efficient Fat Burn Test

As I pitched my tent that August night in 2017, I thought about the challenges ahead. My 63 year-old body was beat. If I continued at this pace, I risked injury. Over my dinner of rationed Ramen noodles, I made my decision: add another day. The next day I hiked under blue skies with bright sun up and over Hays Pass to an alpine valley filled with wildflowers and granite boulders above Golden Lakes. I found a spot next to dancing stream and sat with back against a rock. At 11:20 am the sky darkened. I gazed in awe at the sun with $2.00 plastic glasses purchased in Pinedale. Alone in the wilderness, surrounded by pristine beauty, I was overcome with emotion as moon covered the sun leaving the valley shrouded in darkness. I quit hiking early that day.

The next four days were hard. I reached my car at Big Sandy Opening after eight days, eighty miles of mostly off-trail above timberline hiking, and 12 named passes over 11,000 feet. My pack weighed 20 pounds and I tipped the scale at 166. I lost 5 pounds. If you do the math that is what you would expect to lose burning 65 percent body fat for fuel. Forget the carbo load. This is science. It works.