Crooked Thumb

Photo: The early bird gets the worm: first tracks on the XX Face of Mt. XXXX, Teton Pass, WY 2025

The buried ski track winds through Lodgepole pine and Douglas fir, branches laden with snow. It is 7:30 am, January, 2025. The sun peaks over the Gros Ventre Mountains bathing Teton Pass Ridge in dawn alpenglow.  The air is cold and fresh on this windless morning. On top of the snowpack, feathery crystals of surface hoar sparkle like diamonds in the early sunlight. The winter silence is broken only by the sound of my skis breaking trail through ten inches of new snow. I’m one hour into a six hour ski tour covering eight miles and four thousand vertical feet. With a pace comfortably below my anaerobic threshold, I’m burning predominantly fat for fuel. I have spent two months training for this.

As an energy source, the average adult stores between 1300 and 1500 calories of carbohydrates as glycogen in muscles and as blood glucose. We can perform a moderate workout for 2 to 3 hours using these stored carbohydrates. Also available is an unlimited source of energy of 80,000 calories of stored fat.  At rest, your energy demands come from burning 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 easy to burn carbohydrates rather than complex fatty acids.  When you reach 90% of your maximum heart rate (anaerobic threshold), you are burning 100% carbs. Can you train your body to burn more fat as fuel? Can you increase your anaerobic threshold? Yes to both. Read on.

Understanding your Bodies Energy Systems

There are three main processes that convert energy into adenosine triphosphate (ATP), which provides energy powering muscular activity. 

• ATP–Creatine Phosphate system– At maximum intensity, this system is used for up to 10–15 seconds. The energy source is the small amount of ATP in your muscles. This is the primary system for short, powerful movements such as a 100 m sprint or a difficult rock climbing move. When the power demand subsides, the muscle replenishes its supply of ATP.
• Anaerobic system – This system predominates in supplying energy for intense exercise lasting two to five minutes. The energy source is the conversion of muscle glycogen and blood glucose into ATP. It is the predominant energy system for a 400 m sprint or a 500 foot vertical ski run.
• Aerobic system – This is the long-duration energy system and the most complex of the three energy systems. This system uses oxygen to convert fatty acids into ATP. This energy source relies heavily on our circulatory system to supply oxygen. This makes it slower to act compared to the other two systems.  

Your energy systems work concurrently. When describing activity, it is not a question of which energy system is working, but which predominates. In a long race, or day in the mountains you burn predominantly fat, but without sufficient carbohydrates, fat metabolism is incomplete; your muscles start to burn and you bonk. Fat burns in a carbohydrate flame.

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, I have worked with many clients who 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. Your energy requirement (not including exercise or hard work) is about 1800 calories per day. So keep your carb intake around 600 calories. That is no easy thing, but it works.

 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.

 Training Strategies for Fat Burn Improvement

I train my clients to improve fat burn through interval training. I use a combination of strength, plyometric and aerobic training; sometimes in isolation, other times in combination. Your goal is to improve your fat burn over time. The stronger your cardiovascular system, the more efficient our muscles become in using fatty acids for fuel rather glycogen. You can train your body to burn 80% fat at rest and 60% to 70% fat at moderately intense exercise.

To improve our body’s ability to burn fat, I work within my client’s fat burning zone. This generally at 50 to 70% of your maximum heart rate. Over time, I push those intervals longer and at higher intensities. The body adapts and your fat burning efficiency rises. Training at intervals of 70% to 90% will raise your anaerobic threshold.

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. Having never done a technical mountaineering ascent, at 60 years old he summited the Grand.

Conclusion

Over the years, I have done a lot of research on burning fat for fuel. I have applied that research to myself and my clients. Becoming an efficient fat burner takes time, but it is an achievable goal.

For a seven day of backcountry skiing trip in the Tetons, I generally lose four pounds; all fat. An eight hour ski tour of 4000 vertical feet and 8 miles burns over 4000 calories. On the day, I consume about 500 calories of carbohydrates; the remaining 3500 calories comes from stored fat and carbs. The math works because the science works. 

Please reach out to me at mailto:steve.crookedthumb@gmail.com if you have any questions or I can help you with your nutrition and training.

Afterword

I love backcountry skiing: the solitude, the views, and the unhurried pace. It is perfect for an old geezer. Two days after the storm, the snowpack is solid and the avalanche danger is low: no collapsing, no cracks, no suspect layers. Below my skis is a 1000 foot vertical and 3500 foot long slope of untracked powder snow; one of my favorite lines on Teton Pass. Pushing off with my poles, I turn on my anaerobic energy system and float down the mountain.