Jeff (aka Bronco Billy) is an online endurance coach and veteran ultra runner of nearly two decades. With over 120 ultramarathon finishes, running through the wild and connecting with nature is a meditative experience and a way for him to unplug. Jeff balances his time between mountain running and coaching ultra runners — he somehow still finds the energy for his beautiful wife, three children, dog, two cats, and an organic garden. As Jeff says “Giddyup.”

Career Highlights

  • 1st 2018 Hardrock Hundred Mile Endurance Run, Silverton, Colorado

  • 1st 2018 Pinhoti 100 Mile Endurance Run, Sylacauga, Alabama

  • 1st 2017 Bear 100 Mile Endurance Run, Logan, Utah

  • Coyote Backbone Trail 68-Mile FKT (Fastest Known Time), Santa Monica Mountains, California (2017)

  • 1st 2016 HURT 100 Mile Endurance Run, Oahu, Hawaii

  • 1st 2015 Ultra Fiord 174K, Patagonia, Chile

  • 26 Career Ultra Wins (18 in 100 milers)

  • Double record holder for the fastest combined time of the 2016 Western States® 100-Mile Endurance Run (Squaw Valley to Auburn, California) and the Hardrock Hundred Mile Endurance Run (Silverton, Colorado); 19 days apart


Even as an established world-class runner, Browning studied the high-fat/low-carb diet as a way to improve his nutrition for racing and lifestyle.  We caught up to Browning to ask him why.

NWDC:  What was your nutrition like before you switch to a high-fat/low-carb diet?

Jeff:  I was a vegetarian in my twenties, then in 2004, after having trouble keeping muscle mass and not feeling great, I switched to an organic whole foods diet (clean, grass-fed meats, whole grains, veggies, limiting processed food). I did this for 11 years before finally making the tweak to LCHF lifestyle.

NWDC:  Why did you switch to a keto diet?

Jeff: Initially, I made a switch to cut out sugar to deal with some candida/yeast overgrowth issues I was experiencing. This allowed me to quit feeding the candida with too much glucose in the diet. However, I would clarify, I only eat ketogenic (<50g carbs per day) strategically as a tool occasionally, not 24/7. I initially went keto for 4 weeks to encourage fat adaptation before switching to more of a Primal Blueprint style of eating — 80-200g of carbs per day from paleo/primal sources. So, I’m using fruit and tubers (sweet potato, red potato, etc.) strategically around effort and volume when training.

Browning crossing a river during Hard Rock

NWDC: When did you know you were fat-adapted?

Jeff: After 3 weeks of restricting carbs, I was able to go run for 3 hours with only salt and water and not need calories and not feel like my energy was very low. I could also skip a meal and not crash or feel irritable. I also started testing ketones with a breath meter to see when I was in nutritional ketosis. I also tracked this for a while to experiment with how high I could take my strategic carbs in training and still be in nutritional ketosis.

NWDC:  How has it affected your races?

Jeff: I definitely don’t have major bonks anymore and I recover way faster than my previous high carb self. I have steady energy and consume half the calories in long runs and races compared to how much I consumed per hour as a high carb athlete. I also don’t take calories on runs under 2.5 hours. Only in long runs and races. I also lost 8 pounds when I made the shift to LCHF, which made my strength to weight ratio go up and increase my VO2 Max. I also noticed a marked decrease in inflammation post-races (especially post-100 milers).

NWDC:  What is your nutrition like on race day?

Jeff: Pretty simple. Carbs are on, albeit less per hour than I use to consume before the nutritional shift. My go-to is GU Grape Roctane powder (half serving/one scoop) in a bottle or soft flask between aid stations and a little fruit at the aid stations. I also use a GU gel here and there — mainly strategically when my heart rate is higher (climbs, pushing harder toward the end, etc.). I also have been playing with HVMN ketone esters in tandem with the carb intake during 100s and continue to take Vespa every 2-3 hours on top of the steady drip of GU Roctane in my bottle.

Browning celebrating with spectators on his way to the finish line of his 2018 Hard Rock victory

NWDC: What would you tell someone who is interested in this nutrition program?

Jeff: Read and educate yourself. It’s a great tool for weight loss and encouraging fat adaptation. However, keep in mind ketogenic eating (<50g of carbs) is a conservation diet. Not a great long-term eating strategy if you’re training regularly and have a healthy metabolism. If you’re training, don’t go long-term ketogenic unless you’re trying to manage a metabolic issue and have some insulin resistance. I use keto eating as a tool in 7-14 day windows, or a single day when my training volume is low. Most of the time I’m strategically bumping my carbs up — still sticking to a paleo carb list and timing that increased carb intake around effort and volume. Avoiding grains and sugar in your everyday diet will keep inflammation low and help with faster recovery.

NWDC:  Are there any athletes you would not recommend fat adaption?

Jeff: Anyone dealing with some health issues should talk with a qualified health care professional who specializes in this type of eating strategy. However, if your healthy and are looking to kick on your fat metabolism or lose a few pounds, or simply have more consistent daily energy with no crashes, start playing with an LCHF lifestyle. For most runners who want to try this, you do have to commit to at least a 6-week challenge of eating this way to get the metabolic pathway to burn on-board fat at a higher rate. If you’ve never restricted carbs for several weeks, that pathway is dormant and takes 3-6 weeks — depending on the individual — to really open up and allow the body to make that metabolic shift. However, after that initial adaptation phase of eating ketogenic and keeping carb intake low, you can start to shift to a maintenance eating strategy of 80-200g of carbs from paleo sources and you’ll keep your insulin relatively stable and also recover faster from harder workouts, keep glycogen topped off and have pop in your workouts. My main maintenance diet is Primal Blueprint (

Jeff’s Sponsors:

Patagonia, Altra, GU Energy Labs, Squirrel’s Nut Butter Anti-Chafe, HVMN, Vespa, Suunto, Rudy Project Eyewear, Pro-tec Athletics, Trail Butter


Personal website:


Instagram: GoBroncoBilly

Twitter: GoBroncoBilly

All pictures from Paul Nelson