Effective Fat Burning for Energy Will Lower Your Times and Shed Weight

by Mark Cucuzzella, M.D.

There is a scene from “The Matrix” where Morpheus shows Neo two pills.

“This is your last chance. After this, there is no turning back. You take the blue pill – the story ends, you wake up in your bed and believe whatever you want to believe. You take the red pill – you stay in Wonderland and I show you how deep the rabbit hole goes.”

In the Shepherdstown  Chronicle’s New Year edition, 25-year-old Shane Harris was featured and boldly announced his goal of running faster to achieve peak performance on his military Fitness Test. The majority of the test is your ability to run fast.

As a fellow soldier now developing programs for the United States Air Force  on running performance improvement, I challenged Shane to take the red pill. Even more important than taking the red pill of ditching the big bulky running shoes and transitioning to one with less cushion is swallowing a really bitter red pill- you must run slower to get faster.

Shane and I met in early February and shared his goal. He trusted me and took a chance on the red pill. Shane became a student and piled on the homework and simple training tools, the most important of which was a heart rate monitor.

For running you need to develop the correct system – the aerobic system. This is the highly efficient system utilizing oxygen, glucose and fat metabolism. The modern analogy is this: each of us is blessed with a hybrid engine, actually millions of hybrid engines at the muscular level. The electric engine is your fat burning aerobic system – highly efficient and can run all day on minimal added fuel. It is resilient to breaking down.

In your body this is fat metabolism at the mitochondrial level of your muscles. The less efficient but more readily available engine is the gas or glucose engine. We are constantly mixing and we always need some gas in the tank. The proportions of electric and gas shift as the effort and heart rate go up. The harder and faster the more gas and less electric.

A bird can migrate 7,000 miles without a Powerbar because they are almost exclusively fat burning. If they go a little too fast, they’ll fail.

If you have ever driven a Prius, you see the subtle mixing of gas (glucose) and electric (fat burning) which you cannot detect as the driver. Your body is doing this all the time in exercise. You want more electric. Any activity lasting more than a couple hours is largely electric.

Many of us run too hard and constantly use and replenish the easily accessed glucose tank which can last no more than 90 minutes. When blood glucose levels drop, we crash. Mind and body sense an overwhelming fatigue. Topping off this tank at high levels of exertion is problematic as we do not feel hungry. Blood is being shunted from the gut to the active muscles. Even if you force down calories, it tends to sit in your stomach, or worse, toss back up. To constantly access the deep fat-burning tank you must train correctly.

So how do you build these mitochondrial factories in your muscles so your hybrid engine is at optimum performance?

Your goal is to build a bigger engine – build millions of mitochondrial factories and the roads (capillary blood supply) to deliver the oxygen to them. The heart and lungs are the fuel pump, the engine is the millions of fat and glucose burning mitochondria in the muscles.

The good news is that it is all about running easy. For most highly motivated exercisers, the definition of “easy” is not uniform. What level of effort is “easy” to build and utilize the aerobic system? How can you assess this yourself?

The 180 Formula developed by Dr. Phil Maffetone is still the simplest and best method. The transition from mostly fat burning to glucose burning is the Aerobic Threshold (AT) Heart Rate (HR). You do not run above this until you have fully progressed which often takes six to 12 months.

For most adults you subtract your age from 180. Shane is 25 years old, so 180 25 = 155 Heart Rate.

Shane's results are pretty impressive!

I advised Shane to trust the formula and run under 155 HR, even if it meant walking up a hill. When he applied the monitor in early February at what seemed to him a pedestrian pace of 10:45 a mile, the monitor beeped indicating 155 HR. Shane trusted and slowed down. Ten days later he was running 9:30 a mile below this comfortable 155 HR. Progression continued rapidly, and by March 17 he was running 8:07 a mile at below 155 HR.

Shane continues to progess, and soon he will be running under 8 minutes a mile at an effort he could run for hours since he is using the efficient electric (fat) fuel tank.

A couple more amazing stats: since Shane is using fat as fuel now he is reducing body fat. His weight has dropped from 209 to 195 pounds in six weeks, and all of it fat loss. He works at the Sweet Shop, so this is even more impressive.

His ultimate goal is a top score on the 1.5 mile run test. At the beginning of his experiment he ran the 1.5 mile in 11:26 and just this week he completed it in 9:36 (a time near the top score for the test). So Shane is getting faster, leaner and feeling great and relaxed by running slower and happier.

48 Responses to “Effective Fat Burning for Energy Will Lower Your Times and Shed Weight”

  1. kim says:

    Very Interesting, and it would be nice if it is working.

    Is he still improving his form ?

  2. Hannah says:

    Long time fitness and science nerd here with a couple of questions sparked by the very impressive results…

    My impression was that even when doing lower intensity exercise, the body first depletes (or nearly depletes) the glucose available in the blood and muscle before turning to fat reserves in the muscle and liver. As I understood, this is because glucose can begin glycolysis directly while fatty acids require more processing before being utilized aerobically.

    It would then follow that in order to access the primarily fat burning mode, the length of time spent doing exercise should be increased rather than just decreasing the intensity. For example, hiking for 3 hours will result in more of a fat burn and an increase in stamina than running for 30 minutes will.

    Granted, this is an intuitive rather than professional understanding, but I’m still curious just how the lowered heart rate triggers the metabolic shift between respiration fueled by glucose and respiration fueled by fat.

    How does one trick (if this is the right word) the body into switching to fat just by lowering intensity of exercise? And have any studies been done to show that results like those shown above are actually based on this the shift between burning fat and burning glucose rather than, say, a shift between aerobic and anaerobic respiration?

    And finally, how long does one have to work out at the correct lower heart rate in order to see the benefits described here? If you are already running 30-45 minutes a day, 5-6 times a week, should this average time be maintained even when intensity is decreased?

    Thank you for the interesting post! Brings up a lot of avenues for research that I’ll certainly want to delve into further as I attempt to decrease my own times and body fat without training myself into a pulp.

    • Paul says:


      If shane puts on his shoes stands up and starts running at HR 155 or below. Then yes in the begining he will be burning glycogen almost exclusively. The Fat metabolism system is a bit like an old steam train in that regard… it takes a little while for it to get working. After 5 minutes though the energy will be coming from a mix of glycogen metabolism and fat metabolism… probably still heavily slanted towards glycogen… but after about 20-25 minutes his energy needs will be being meet for the most part by fat metabolism.

      This is also why taking the first 5km of a marathon a bit slower than the rest is a good idea if you havent been able to do a warmup before the start.

      Incedentally the info that you have to run 90 minutes before you start training your fat metabolism probably stems from running those runs just a tick over the AT. for instance my AT is around HR 140… so my Easy Aerobic runs are done at that pace, But i also do a couple of runs a week with a HR at 146-147 These are still Aerobic runs, but they are now primarily using the glycogen stores for fuel, if i want to also target my fat metabolism system in those runs id need to extend them out beyond 90 mins.

  3. Great questions Hannah on a complex topic. Phil Maffetone’s Big Book of Endurance Training and Racing is a good read on the topic.

    My piece from our Freedom’s Run training page has some good info too

    Diet affects this is a significant way also. Stop chasing the carbs, build the roads (capillaries), and be aerobic all day.

    There is an evolving field called “epigenetics” and we can up and down genes based on multiple environmental factors (diet, activity, your profile)…so this is way more complex than we think.

    So bottom line…run in the happy zone! Hard to get hurt that way.


  4. bill k says:

    The NRC experts will let you know more….

  5. Ryan says:

    Two part question: 1. Will this work with someone who has been running for a few years and seems to have hit a plateau? 2. When doing this can you never run at a higher intensity in order to teach your body how to burn correctly? Or are there times that running at a higher intensity can also be worked into the routine?


    • MarkC says:


      Great questions. yes you can plateau when you have reached close to full aerobic development. you can do things to help get you “quick” without running “hard”. these are short quick strides, drills like skipping to wake up elastic recoil, and some dynamic stretching to increase joint range of motion, esp allowing you to extend at the hip.


  6. Ron says:

    OK Doc, I took the red pill yesterday morning. A little background;

    Male, 57, 5’8″, about 147 lbs. Running for the last 30 months (lost about 25 lbs.) working up to 5+ miles 4 times/week, training at 7:30/mile (av. 155+/- BPM) and under 7:00 doing 5Ks. No real injuries, rarely sick, feel great for a slightly overweight old man with CAD. Cardiologist puts me in top 5% of my bracket. Eating fresh fruits and veggies, beans and nuts, no meat. Having a difficult time loosing that last 5-10 lbs., and want to do longer runs plus gain speed, if possible.

    So my target HR is something like 130, correct? Was able to keep my 180+ cadence but found it difficult to stay below 142 or so, which feels like my sweet (happy) spot. At the end of my 5+ miler I was not stressed at all and recovered almost immediately. Feel like I could run 10 miles at that pace.

    So, the closer I get to that 130 BPM the sooner I’ll see real results? Should I be increasing my miles and/or doing more run days per week, or neither?

    I’m in this for the long haul Morphius.

  7. Ken Fisher says:

    Dr. Mark,
    I attended the weekend training session at TRT with John. He mentioned the Maffetone method and I came back home, did some research and began to try it out. My times have increased, and my body fat has certainly decreased, but I have a question. I also play hockey which is an anaerobic sport. Is this having a negative effect on me? Is this sport conflicting or delaying the effects of the Maffetone method?
    Thanks, and see you in Oct again!

    • MarkC says:


      The hockey is great. this is FUN and works your balance and neuromuscular quickness without a taxing anaerobic load. just don’t get hit in the face by a puck.


  8. Tim White says:

    So does one need to do this easy running for a specified amount of time? I am assuming 30 minutes of easy running a day won’t cut it.


    • MarkC says:


      at least 30 minutes, preferably work up to 60 min 5-6 times a week. you will not feel tired with this type of running. it adds energy to your day.


  9. Ron says:

    So Mark, if that 60 minutes 5-6 times a week is not possible would it just take longer to see the results, as my regime only gives me 4 days/week? As one’s pace increases with time stick with the 60 minutes and increase the distance?

    And most of what I’ve read about this has studies with guys in their 20’s. How much of a different should a man in his later 50’s expect to see?

  10. Mark Finnegan says:

    I’m a 50 yo physician from Phila. Training for NYC Marathon.
    Keeping HR 130-135 but pace is 11-12min/mile. Should I be doing
    Hill or Speed workouts? I’ve been using HR monitor for ~3weeks.
    When do you start to see results?
    Mark Finnegan

  11. Chris Edmonds says:

    Really interesting article. Found it while researching heart-rate monitors. Figure I’ll ask: What models/makes/etc. do you recommend that has the features needed for this kind of training?

  12. Alan says:

    Thanks for the great read! Which shall I prioritize the aerobic engine or the 180 cadence (less injuries). To remain at my aerobic level, cadence slows down causing tenderness in the hip joints as well as knee joints. At a faster cadence, I go into anaerobic. Thank you in advance.

    • JoshD says:

      You probably need to walk/hike/easy bike ride for awhile (still wear the hrm) while doing aerobic track intervals to work on form. Your aerobic system is very much underdeveloped and you should stay away from anaerobic until your aerobic fitness is fully developed. You are probably feeling little injuries in your hips and knee’s not just because of crap form but probably from to much stress induced running in the past.

  13. Andrew says:

    I have a question regarding this method of training. I have been using maffetone’s method for around 6 months now with fantastic results! My question is this: the post says that your maximum aerobic function heart rate can be sustained for hours, is this really true? My legs are really starting to feel tired as my pace at this heart rate continues, and I wonder how easily I could maintain this pace for hours on end. Thanks!

    • MarkC says:


      fatigue is metabolic and mechanical (muscle fatigue). many get fatigued from the gas tank being empty. with Maffetone aerobic speed you are like a migrating bird. you do need to add some glucose to intake for really long walks/rides/runs but the majority of energy comes from fat burning pathways

      Running is fatiguing in other ways too so your limit may be the muscle/tendon fatigue and there may be some inefficiencies in your stride that can be worked on.

      Example i have not swam in years and even though I’m aerobically fit i’ll fatigue pretty quick with the movement pattern i’m not used to yet.

      Keep progressing. We are all and experiment of 1.


  14. Paul says:


    Ill back up what Mark said. On the back of a bunch of Aerobic training I ran an outstanding Marathon PB -15min and was able to bounce back after it with not too much in the way of DOMS.

    A month later i ran a debut Ultra of 63 km. My HM splits were 1:53, 1:52, 1:51 I was one of only very few that was able to maintain (or even increase the pace slowly) across the whole race. I attribute that to all the Aerobic work id done in the buildup to the marathon. What i hadnt done however is a lot of the real long runs that are traditional for ultra runners, Instead just my regular marathon long runs of 22m.

    I am pretty sure that i could have kept up that pace around the 1:50 per HM a lot longer if it wasnt for my legs, they were starting to show the strain of the unaccoustemed length of time running, and mechanically id probably no have been able to handle much more without either having to significantly reduce the pace, or run myself into an injury.

  15. Kathleen says:

    I just came across this article yesterday and I felt it was just what I was looking for. As a soon to be 60 y/o female who is trying to maintain a 6 year 80 pound weight loss, I put the principles to work yesterday on my 5 mile run (25 miles per week). Like the rest of you, I had to run slower than usual to keep my HR around 130. Instead of a 43 minute run, it became a 53 minute run. Today it was a 49 minute run. (Perhaps because I didn’t start my morning with a 1 mile swim which I often do.) I am very motivated to stay on this course through the rest of this year and I will update with stats. Thanks Mark for giving me a new goal to work towards.

  16. Frederick says:

    Hello Mark,
    I am a competitive ultramarathoner who has been interested in midfoot landing for years, trying it off and on. I noticed at the North Coast National Championship 24-Hour Run last year that while Rick, Roy, and Harvey started out landing on their forefeet, by the end, they had all been landing on their heels for hours. By the end of the race, there was not a single forefoot striker on the course. Phil, the runner Rick mentioned in his other post, and the rest of the top 5 runners (beside Harvey), are all full-time heel-landers.

    What is your take on midfoot landing in minimalist shoes for ultrarunners? I keep thinking that this is how our ancestors must have landed while doing long runs, and have been going back and forth with this idea of sandaled or moccasin-wearing early humans having to land with a midfoot strike instead of a forefoot strike.

    In the last 20 years, I have only seen one ultrarunner, Rudy Afanador, the former national 24-hour champion from NY, run an entire 100+mile race while landing on his forefoot. Six years or so ago he was injured and now cannot compete well, and so I have not seen a single athlete who lands on the forefoot during runs of that length. Midfoot landing, however, seems a lot more sustainable. I would love to hear your thoughts about this, and a recommendation or two for a good shoe for long distances.

    Thank you very much.

  17. Kathleen says:

    Hi Frederick,
    Check out OESHSHOES.com. I think it just might be what you’re looking for.

  18. BARRY says:

    I’m 43, 6ft1, 13stone, 17.3% body fat. Three weeks ago I decided it was time to dedicate all of my time to getting a six pack, I don’t work so I have the time. I train with a world pro kick boxing trainer and fighter, my weight has stayed the same, my muscles are fuller and my body fat has reduced; I changed my diet massively, that is a chapter on its own. I am training with him at over 100% max hear rate, I drop to the deck regularly during training and feel sick quite regularly. Anyway, I bought a heart monitor because I want to run 4 times per week, this 70% situation is embarrassing, I’m a big guy with an overall appearance of really good, but this 70% theme, I only walk, I can break into a stupidly slow jog downhill. My heart rate at rest is 60bpm. Can anybody offer me some advice please, it took me 75 minutes to do 5 miles, ok the terrain was huge hills but nevertheless so embarrassing, I may as well have walked in a three piece suite and tie, ha! Help guys…

    • MarkC says:


      aerobic development is different for the high intensity stuff and you must go slow at first. it takes months but your body will transform as all the metabolic changes occur. Buy the books from Phil Maffetone.


    • JoshDreher says:

      Barry, one of the big things to understand is stress. If you overdue it at the gym (over 100% max heart rate!?!) you are overstressing your system which may actually add fat to your lower stomach because cortisol (the stress hormone) directs fat from other areas of the body to the stomach and can store dangerous molecules like cytokines which are incredibly toxic. I used to rock climb 4 days a week, bike, and run at full effort 4-5 times a week until I got sick, injured in all the sports I was doing and depressed because of all of my injuries. After following Phil’s method for a few months things healed up, I lost more weight and my speeds increased and are still increasing. With regards to your running time, don’t get frustrated just stick with it. Think of it as building a base for lifelong fitnes. Know that building the aerobic base takes some time but you will get faster and faster to the point where you will need to do aerobic intervals because you can’t run at your max aerobic thresh-hold all the time. You will also lose weight because instead of burning carbs and producing lactate you’ll burn fat! If you want to lose weight you need to do almost all of your workouts for awhile in the aerobic zone.
      Buy Phil’ book. It will change your life.

  19. BARRY says:

    update… body fat 16.9percent this morning, hoorah for diet and exercise!

  20. Cheryl says:

    Dr Mark,
    I have been following your site as well as SocDoc and have read Dr. Maffetone’s Big Book of Endurance Training and Racing. After attending one of Blaise Deboise’ courses last June I began my running transition into a natural running form (after many years off followed by a successful bout of sprint triathlons followed by several years of injuries–now known simply as muscle imbalances). I have been working hard at form and establishing my aerobic base. My pace has improved from 10:15 min/mile to 8:55 min/mile. I have high hopes for completing a half marathon this spring and a full in the fall. But, now I feel quite lost as how to train for this. I understand that at some point I need to add some anaerobic training in but in using the heart rate training, how high is a target rate for my 135 aerobic target? AND can you recommend a training schedule that takes into account the importance of heart rate monitoring and uses this as a guide? Based on your last article I plan to have fun with my training but I need to be mentally and physically ready for the runs. Thanks for your help and for the great website!

  21. Nicolas says:

    Dr. Mark,

    I must sympathize with Barry. The speed needed to stay in the target rate range is, in my case, barely faster than walking (slower uphill). This becomes more a training of the ego than the body. I love it!

    Thank you for the great post and responses.

  22. BARRY says:

    And now more emotional pain, ha! Am doing more training and body fat has crept back up to 17.5%.

    All this hard work, could do with more gains…

  23. Kathleen says:

    Since one of the reasons I’m using the method talked about in this article is to lose a little weight, I’d love some analysis of doing a workout in a fasted or non fasted state. Currently I use a pre and post workout product from the VegaSport line. (Pre-workout Energizer & Recovery Accelerator) The pre has 12 grams of sugar and the post has 15. Is it hampering me by preventing my body access to its fat storage?

    • MarkC says:

      try to do the run with the eating on the front end but after longer efforts replete the glycogen stores and repair tissue with good mix of healthy carb, high quality protein, and healthy fat. I like real food. chocolate milk is a simple drink too. Mark

  24. Scott says:

    I am a 27 year old male with many triathlons of all distances under my belt. I started the Maffetone method at the beginning of July. The first mile in my runs has gone from 9:48 to 7:46, and my average pace has dropped from the upper 10:00 range over 3 miles to 8:11 over 4 miles, all in about 7 weeks. First off, I’ve been waiting for my gains to taper off, but they haven’t yet. Given that I’ve never trained by heart rate before this, and I’ve always pushed myself to what must be a higher heart rate than I’m doing now and suffered injuries as a result, could I really expect to continue to see improvements for half a year or more?

    Second, are there any resources to help me determine my race paces? Without doing speedwork, I think it will be difficult to judge how hard to push myself in races ranging from 5k to Ironman distance. Any advice?


    • MarkC says:


      this is great…you are getting it! start to add strides and drills to work the speed and coordinataion without running “hard”. when you are plateauing start to do some lactate threshold running once or twice a week. these are sustained runs at about 10k pace or a bit slower. you will develop relaxed speed, that is the goal.


  25. Tyson park says:

    I’m 71yrs young & started to run marathon this yr completed three so far. I ran San Francisco marathon in barefoot. Because of foot Pains, I started to run with barefoot around three months & felt good for 10 miles runsf but regretfully found out 10 miles was no 26 miles. Every step was so painful in last 6 miles. Golden Gate surface was so cold, slippery, sharp steel plates $ lost total foot sensory. I wished I knew! I was 9th in age group ( 4th LA marathon, 2nd OC marathon & 1 st LA half marathon ). My goal really was to improve PR for Boston marathon 2013 from 4:22 time. My chance for Boston 2013 is not good but I’m very proud of my accomplishment. I really like to run Boston marathon in barefoot after painful experience of SF marathon. I ran along with Dean Kanazes for few miles until Golden Gate bridge. His running style was very smooth.& efficient. I run almost every day in barefoot 5-10 miles. Clearly I’m a follower of Dr. Maffetone & Dr. Mark without them I could not be as I’m now. Overall benefit from barefoot running is incredible particularly for old age group. I just hope that runners old and young would not pay attention other so called experts. Just follow these two Drs. & you will save $, time,& injuries.

    • MarkC says:

      Wow…thanks for the inspiration to others Tyson. I spoke on a panel with Dean today. small world and yes Dean runs with efficiency or he would be done by now, but he is getting better. Boston is probably a little kinder for the bare soles than SF but there are lots of potholes, manholes, and grit in the City. Big Sur would be a beautiful barefoot run.

  26. NEW runner following Run Your Butt Off! wearing minimalist shoes. I run on a treadmill at the gym and do okay in just socks for part of it.

    Can I combine both programs just by watching my HR and running for longer than 30 minutes/4 times a week?

    I also play volleyball :-) We’re not serious about our volleyball but we are serious about our play!

  27. Chris says:

    I have been running 35 mins 4 times a week using the 180 methos and I have not improved at all. I have been doing this for just over 3 months and I am still doing around 10 mins per mile.

    I was a regular runner before moving to the 180 method. Should I be seeing something by now. I keep going thinking ‘today will be the day’ when mt time drops but nothing……..help !

    • Alan says:

      My first thought is that if you are doing the same thing over and over your body will stop adapting. I started doing this type of running over 4 months ago and have made very strong gains and run a 10k PR with almost no additional faster running other than some short sprints (8-10sec) once a week. BUT, my mileage has gone from 8 to ten miles a week up to around 30. Even though I have maintained a consistent effort for most of the runs and the mileage is going up the paces have been getting faster and faster. I also decided not to fuel during any runs including the long runs. I can run two hours with just water/electrolytes and feel pretty good.

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  29. flokon says:

    Hi there,
    I am really interested in this method. I clock most of my mileage at 80-82%HRM, which happens to be 180-age. Although a bit faster feels better from a running form point of view, I stick to 180-age because it seems as like I can go on forever at that pace (5:30/km)
    I have a health-related question though: At 6’3″ I weigh 75kg and my body fat ranges from 5-6% through the year. Isn’t it unhealthy to burn so much fat all the time? I eat mostly carbs (oats, brown rice, sweet potatoes, quinoa), fruit (bananas), and veggies (broccoli, cauliflower, carrots, mushrooms). 2-3 times a week I have beef, chicken or fish to cover my protein, and fat needs.
    Is it possible to have too little body fat to actually benefit from Phil Maffetone’s approach, and is it possible to actually harm ones body in the process of running off of too little body fat?


    • MarkC says:

      great question. too low body fat is unhealthy for endocrine function so listen to how you feel. if you are fatiqued and not recovering get a little more fat on your frame. if you feel good continue the healthy eating patterns, but suggest adding more healthy fats daily. also the method of body fat measurement is important as many methods are off and 5-6% really low. best, Mark

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