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HMB
,Created page with "{{DISPLAYTITLE:HMB For Runners}} HMB is a supplement that may help preserve muscle during weight loss, something that is typically quite difficult. HMB might improve fat loss,..."
{{DISPLAYTITLE:HMB For Runners}}
HMB is a supplement that may help preserve muscle during weight loss, something that is typically quite difficult. HMB might improve fat loss, increase muscle gain, and there's slight evidence that it might increase aerobic performance. HMB appears safe at the recommended doses and is not banned. HMB should be taken to time with periods when muscles loss may occur, such as exercise or fasting. I would be cautious about taking HMB before a critical race, as the breakdown of muscle may provide a valuable energy source.
=What is HMB?=
HMB, or "β-Hydroxy β-methylbutyric acid" to give it its full name<ref name="HMBPubChem"/>, is naturally produced in the body as the amino acid leucine is metabolized<ref name="MolfinoGioia2013"/>. It's been shown that leucine controls protein synthesis and metabolism<ref name="NortonLayman2006"/>, and it seems that one mechanism of action is via the HMB metabolite<ref name="NissenSharp1996"/>. My personal interpretation is that HMB tricks the body into acting as if it had consumed large quantities of protein, activating protein synthesis and inhibiting protein metabolism.
=HMB Benefits=
There are several benefits to HMB that make it of interest to runners.
* HMB inhibits muscle breakdown (proteolysis) after training<ref name="NissenSharp1996"/>, in old age<ref name="WuXia2015"/>, bed rest<ref name="DeutzPereira2013"/>, and muscle wasting conditions such as AIDS and cancer<ref name="Hasselgren2014"/>. Most importantly for athletes, HMB reduces muscle loss during calorie restricted training<ref name="ParkHenning2013"/>.
* HMB reduces muscle damage after endurance running (20Km/13 miles)<ref name="KnitterPanton2000"/>.
* HMB enhances the fat lose effects of exercise<ref name="StoutFukuda2015"/>.
* Not only does HMB reduce protein losses, it also increases protein synthesis, even in fasting subjects<ref name="WilkinsonHossain2013"/>. Subjects in that study were recreationally active, but not formally training. They did not perform heavy exercise for 72 hours and were overnight fasted. This is really interesting as it indicates that HMB can improve protein synthesis in the absence of recent exercise stress or protein intake.
* I found one study that showed two weeks of HMB reduce [[Lactate]] accumulation and increased VO<sub>2</sub> at 2 mM Lactate after <ref name="VukovichDreifort2001"/>. Personally, I suspect any improvement is probably due to changes in body composition.
* HMB may improve some markers of cardiovascular health, such as blood pressure and LDL cholesterol<ref name="NissenSharp2000"/>.
* There's some evidence from animal studies that HMB may reduce insulin resistance<ref name="SharawyEl-Awady2016"/><ref name="FuBruckbauer2015"/>, though in high doses (equivalent of >50g/day in humans) one study found increased insulin resistance<ref name="YonamineTeixeira2014"/>.
* HMB doesn't raise insulin levels<ref name="WilkinsonHossain2013"/>, unlike protein, so it doesn't inhibit fat loss (lipolysis.) This is critical given it's use to improve fat loss.
=How I take HMB =
This isn't medical advice, just my approach that you can use as a starting point. I'm continually tweaking my training and nutrition, so by the time I've finished writing this it's likely to be slightly different! My approach assumes I'm trying to reduce my body fat while keeping or increasing lean mass, which is fairly normal for me. The calcium form of HMB (the cheapest and most widely tested) peaks in the blood about 30 minutes after consumption<ref name="WilkinsonHossain2013"/>, and has a half-life of about 2.5hours<ref name="FullerSharp2010"/>. This means that timing seems to be pretty important.
* I don't follow the standard recommendation of 1g, 3 times per day. I did that initially, and I seem to have much better results by timing the doses more carefully based on the research. I'm also typically taking more than the 3g/day.
* I've found that intermittent fasting (IF) seems to work best for me to lose weight or just keep my weight under control. I often joke I have the genes of a natural athlete, but sadly my natural sport is sumo wrestling. I tend to use the 16:8 pattern of 16 hours of fasting and 8 hours of eating. However, this is a little modified depending on training. I typically break my fast mid-late morning.
* The combination of IF, HMB, high [[Protein]] intake and [[Vitamin C]] seems to work remarkably well for me. I aim for more than 3g/Kg of protein per day, which is on the high end of the recommendations for a calorie restricted athlete. I typically take 1-2g/day of Vitamin C, which seems to make a huge difference to my ability to adapt to endurance training. Without it, my ability to build up my distance seems seriously impaired.
* I usually take ~1g of HMB in a dose, either mixed in a calorie free electrolyte drink or in a protein smoothie. The taste is a little musty but not unpleasant to me. I've had no GI issues with HMB, nor heard of any being reported.
* On rest days, I'll take HMB while fasting, often with some Vitamin C. I aim to take HMB about every 3-5 hour to push my body towards burning body fat rather than muscle. While I'd like to think the HMB will actually build muscle, I suspect that being fasted and calorie restricted makes this unlikely at this point in my day.
* I break my fast on rest days with Casein protein with HMB and Vitamin C. The idea here is to provide protein without raising insulin too much. I'm hopeful that I can extend the fat burning into this early part of the post-fast. Casein has a lower insulin response than whey<ref name="ReitelsederAgergaard2011"/>. That study showed casein resulted in a lower insulin response from 15 to 60 minutes, a peak insulin of ~110 v 180 for whey (pmol/L), and with a total insulin response (area under the curve) of 15.6 v 18.5 for whey.
* On rest days I will often do a brief [[High Intensity Interval Training]] session on the bike trainer. This is typically 4-6x 12 seconds at 7-9 watts/Kg with 2-minute recoveries. I mostly time the session around the HMB intake.
* On training days, I often will take HMB, with ~5g of Arginine, ~5g of Citrulline-Malate, and 6-8oz beetroot juice just before starting running. The goal of the other ingredients is to boost blood supply to the muscles.
* My nutrition during the run varies, but typically I refuel every 60-120 minutes. Sometimes my "fuel" will be just an HMB/Vitamin C dose in an electrolyte drink, but doing a marathon+ length training run without calories is tough. I'll often take 5-10g of whey protein as fuel, which makes a huge difference (possibly placebo) to my performance. If I'm feeling the need, often on back to back marathon+ days I'll add 5-10g sugar to the mix. My aim is to stay in sufficient calorie deficit that I can convince myself I'm still fasting.
* What I do at the end of the run depends on timing. If I'm ready to end the fast, I'll typically make a hot chocolate with 1 tablespoon pure cocoa, 25g whey, and 8oz of milk. If the fast is continuing then it will just be HMB and vitamin C.
* I finish my eating period with Casein protein, milk, and sometimes eggs, but without HMB. My goal is to have a supply of protein available for the early part of the fast, including the initial sleep period.
* I take an HMB & Vitamin C dose just before sleeping, typically 1-3 hours after starting the fast. This is to keep the HMB levels up overnight to prevent muscle metabolism.
* Depending on how I'm feeling, I sometimes take a dose of HMB in the middle of the night.
=HMB Forms=
HMB is available as a calcium salt or as a free acid, with the free acid resulting in a more rapid rise in blood HMB levels, has nearly twice the area under the curve, and has 25% greater utilization<ref name="FullerSharp2010"/>. The free acid has a half life of ~3 hours and the calcium salt is ~2.5 hours<ref name="FullerSharp2010"/>. However, most research has been on the calcium salt, and the free acid form is more expensive, so personally I've only used the calcium salt.
/
A comparison of Calcium (open circles) with oral free acid (solid circles), and sublingual free acid (triangles) of HMB.
=HMB Safety=
Since it's first use as a nutritional supplement in 1997, HMB has been extensively studied, and found to be safe in both human and rodents<ref name="WilsonFitschen2013"/>. There was one study that found high doses of HMB, the equivalent of over 50g/day in humans, increased insulin resistance<ref name="YonamineTeixeira2014"/>, though other studies show improved insulin resistance at typical levels (see above). However, contamination of supplements is an issue, with at least one athlete testing positive due to taking an HMB supplement<ref name="wada"/>.
=References=
<references>
<ref name="wada">wada-ama.org !!work!!, 6 December 2019 !!access-date!!, https://www.wada-ama.org/sites/default/files/resources/files/cas_2008_a_1510_despres.pdf</ref>
<ref name="StoutFukuda2015">Jeffrey R. Stout, David H. Fukuda, Kristina L. Kendall, Abbie E. Smith-Ryan, Jordan R. Moon, Jay R. Hoffman, β-Hydroxy-β-methylbutyrate (HMB) supplementation and resistance exercise significantly reduce abdominal adiposity in healthy elderly men, Experimental Gerontology, volume 64, 2015, pages 33–34, ISSN [http://www.worldcat.org/issn/05315565 05315565], doi [http://dx.doi.org/10.1016/j.exger.2015.02.012 10.1016/j.exger.2015.02.012]</ref>
<ref name="NortonLayman2006">Layne E. Norton, Donald K. Layman, Leucine Regulates Translation Initiation of Protein Synthesis in Skeletal Muscle after Exercise, The Journal of Nutrition, volume 136, issue 2, 2006, pages 533S–537S, ISSN [http://www.worldcat.org/issn/0022-3166 0022-3166], doi [http://dx.doi.org/10.1093/jn/136.2.533S 10.1093/jn/136.2.533S]</ref>
<ref name="FullerSharp2010">John C. Fuller, Rick L. Sharp, Hector F. Angus, Shawn M. Baier, John A. Rathmacher, Free acid gel form of β-hydroxy-β-methylbutyrate (HMB) improves HMB clearance from plasma in human subjects compared with the calcium HMB salt, British Journal of Nutrition, volume 105, issue 3, 2010, pages 367–372, ISSN [http://www.worldcat.org/issn/0007-1145 0007-1145], doi [http://dx.doi.org/10.1017/S0007114510003582 10.1017/S0007114510003582]</ref>
<ref name="MolfinoGioia2013">Alessio Molfino, Gianfranco Gioia, Filippo Rossi Fanelli, Maurizio Muscaritoli, Beta-hydroxy-beta-methylbutyrate supplementation in health and disease: a systematic review of randomized trials, Amino Acids, volume 45, issue 6, 2013, pages 1273–1292, ISSN [http://www.worldcat.org/issn/0939-4451 0939-4451], doi [http://dx.doi.org/10.1007/s00726-013-1592-z 10.1007/s00726-013-1592-z]</ref>
<ref name="HMBPubChem">National Center for Biotechnology Information. PubChem Database. beta-Hydroxyisovaleric acid, CID=69362, https://pubchem.ncbi.nlm.nih.gov/compound/beta-Hydroxyisovaleric-acid (accessed on Dec. 6, 2019)</ref>
<ref name="VukovichDreifort2001">Matthew D. Vukovich, Geri D. Dreifort, Effect of β-Hydroxy β-Methylbutyrate on the Onset of Blood Lactate Accumulation and Vo2peak in Endurance-Trained Cyclists, Journal of Strength and Conditioning Research, volume 15, issue 4, 2001, pages 491–497, ISSN [http://www.worldcat.org/issn/1064-8011 1064-8011], doi [http://dx.doi.org/10.1519/00124278-200111000-00015 10.1519/00124278-200111000-00015]</ref>
<ref name="NissenSharp1996">S. Nissen, R. Sharp, M. Ray, J. A. Rathmacher, D. Rice, J. C. Fuller, A. S. Connelly, N. Abumrad, Effect of leucine metabolite β-hydroxy-β-methylbutyrate on muscle metabolism during resistance-exercise training, Journal of Applied Physiology, volume 81, issue 5, 1996, pages 2095–2104, ISSN [http://www.worldcat.org/issn/8750-7587 8750-7587], doi [http://dx.doi.org/10.1152/jappl.1996.81.5.2095 10.1152/jappl.1996.81.5.2095]</ref>
<ref name="WuXia2015">Hongmei Wu, Yang Xia, Jin Jiang, Huanmin Du, Xiaoyan Guo, Xing Liu, Chunlei Li, Guowei Huang, Kaijun Niu, Effect of beta-hydroxy-beta-methylbutyrate supplementation on muscle loss in older adults: A systematic review and meta-analysis, Archives of Gerontology and Geriatrics, volume 61, issue 2, 2015, pages 168–175, ISSN [http://www.worldcat.org/issn/01674943 01674943], doi [http://dx.doi.org/10.1016/j.archger.2015.06.020 10.1016/j.archger.2015.06.020]</ref>
<ref name="Hasselgren2014">Per-Olof Hasselgren, β-Hydroxy-β-methylbutyrate (HMB) and prevention of muscle wasting, Metabolism, volume 63, issue 1, 2014, pages 5–8, ISSN [http://www.worldcat.org/issn/00260495 00260495], doi [http://dx.doi.org/10.1016/j.metabol.2013.09.015 10.1016/j.metabol.2013.09.015]</ref>
<ref name="DeutzPereira2013">Nicolaas E.P. Deutz, Suzette L. Pereira, Nicholas P. Hays, Jeffery S. Oliver, Neile K. Edens, Chris M. Evans, Robert R. Wolfe, Effect of β-hydroxy-β-methylbutyrate (HMB) on lean body mass during 10 days of bed rest in older adults, Clinical Nutrition, volume 32, issue 5, 2013, pages 704–712, ISSN [http://www.worldcat.org/issn/02615614 02615614], doi [http://dx.doi.org/10.1016/j.clnu.2013.02.011 10.1016/j.clnu.2013.02.011]</ref>
<ref name="ParkHenning2013">Bong-Sup Park, Paul C. Henning, Samuel C. Grant, Won Jun Lee, Sang-Rok Lee, Bahram H. Arjmandi, Jeong-Su Kim, HMB attenuates muscle loss during sustained energy deficit induced by calorie restriction and endurance exercise, Metabolism, volume 62, issue 12, 2013, pages 1718–1729, ISSN [http://www.worldcat.org/issn/00260495 00260495], doi [http://dx.doi.org/10.1016/j.metabol.2013.06.005 10.1016/j.metabol.2013.06.005]</ref>
<ref name="KnitterPanton2000">A. E. Knitter, L. Panton, J. A. Rathmacher, A. Petersen, R. Sharp, Effects of β-hydroxy-β-methylbutyrate on muscle damage after a prolonged run, Journal of Applied Physiology, volume 89, issue 4, 2000, pages 1340–1344, ISSN [http://www.worldcat.org/issn/8750-7587 8750-7587], doi [http://dx.doi.org/10.1152/jappl.2000.89.4.1340 10.1152/jappl.2000.89.4.1340]</ref>
<ref name="NissenSharp2000">S. Nissen, R. L. Sharp, L. Panton, M. Vukovich, S. Trappe, J. C. Fuller, β-Hydroxy-β-Methylbutyrate (HMB) Supplementation in Humans Is Safe and May Decrease Cardiovascular Risk Factors, The Journal of Nutrition, volume 130, issue 8, 2000, pages 1937–1945, ISSN [http://www.worldcat.org/issn/0022-3166 0022-3166], doi [http://dx.doi.org/10.1093/jn/130.8.1937 10.1093/jn/130.8.1937]</ref>
<ref name="WilsonFitschen2013">Jacob M Wilson, Peter J Fitschen, Bill Campbell, Gabriel J Wilson, Nelo Zanchi, Lem Taylor, Colin Wilborn, Douglas S Kalman, Jeffrey R Stout, Jay R Hoffman, Tim N Ziegenfuss, Hector L Lopez, Richard B Kreider, Abbie E Smith-Ryan, Jose Antonio, International Society of Sports Nutrition Position Stand: beta-hydroxy-beta-methylbutyrate (HMB), Journal of the International Society of Sports Nutrition, volume 10, issue 1, 2013, ISSN [http://www.worldcat.org/issn/1550-2783 1550-2783], doi [http://dx.doi.org/10.1186/1550-2783-10-6 10.1186/1550-2783-10-6]</ref>
<ref name="SharawyEl-Awady2016">Maha H. Sharawy, Mohammed S. El-Awady, Nirmeen Megahed, Nariman M. Gameil, The ergogenic supplement β-hydroxy-β-methylbutyrate (HMB) attenuates insulin resistance through suppressing GLUT-2 in rat liver, Canadian Journal of Physiology and Pharmacology, volume 94, issue 5, 2016, pages 488–497, ISSN [http://www.worldcat.org/issn/0008-4212 0008-4212], doi [http://dx.doi.org/10.1139/cjpp-2015-0385 10.1139/cjpp-2015-0385]</ref>
<ref name="FuBruckbauer2015">Lizhi Fu, Antje Bruckbauer, Fenfen Li, Qiang Cao, Xin Cui, Rui Wu, Hang Shi, Michael B. Zemel, Bingzhong Xue, Leucine amplifies the effects of metformin on insulin sensitivity and glycemic control in diet-induced obese mice, Metabolism, volume 64, issue 7, 2015, pages 845–856, ISSN [http://www.worldcat.org/issn/00260495 00260495], doi [http://dx.doi.org/10.1016/j.metabol.2015.03.007 10.1016/j.metabol.2015.03.007]</ref>
<ref name="YonamineTeixeira2014">C. Y. Yonamine, S. S. Teixeira, R. S. Campello, F. Gerlinger-Romero, C. F. Rodrigues, L. Guimarães-Ferreira, U. F. Machado, M. T. Nunes, Beta hydroxy beta methylbutyrate supplementation impairs peripheral insulin sensitivity in healthy sedentary Wistar rats, Acta Physiologica, volume 212, issue 1, 2014, pages 62–74, ISSN [http://www.worldcat.org/issn/17481708 17481708], doi [http://dx.doi.org/10.1111/apha.12336 10.1111/apha.12336]</ref>
<ref name="WilkinsonHossain2013">D. J. Wilkinson, T. Hossain, D. S. Hill, B. E. Phillips, H. Crossland, J. Williams, P. Loughna, T. A. Churchward-Venne, L. Breen, S. M. Phillips, T. Etheridge, J. A. Rathmacher, K. Smith, N. J. Szewczyk, P. J. Atherton, Effects of leucine and its metabolite β-hydroxy-β-methylbutyrate on human skeletal muscle protein metabolism, The Journal of Physiology, volume 591, issue 11, 2013, pages 2911–2923, ISSN [http://www.worldcat.org/issn/00223751 00223751], doi [http://dx.doi.org/10.1113/jphysiol.2013.253203 10.1113/jphysiol.2013.253203]</ref>
<ref name="ReitelsederAgergaard2011">Søren Reitelseder, Jakob Agergaard, Simon Doessing, Ida C. Helmark, Peter Lund, Niels B. Kristensen, Jan Frystyk, Allan Flyvbjerg, Peter Schjerling, Gerrit van Hall, Michael Kjaer, Lars Holm, Whey and casein labeled with l-[1-13C]leucine and muscle protein synthesis: effect of resistance exercise and protein ingestion, American Journal of Physiology-Endocrinology and Metabolism, volume 300, issue 1, 2011, pages E231–E242, ISSN [http://www.worldcat.org/issn/0193-1849 0193-1849], doi [http://dx.doi.org/10.1152/ajpendo.00513.2010 10.1152/ajpendo.00513.2010]</ref>
</references>
HMB is a supplement that may help preserve muscle during weight loss, something that is typically quite difficult. HMB might improve fat loss, increase muscle gain, and there's slight evidence that it might increase aerobic performance. HMB appears safe at the recommended doses and is not banned. HMB should be taken to time with periods when muscles loss may occur, such as exercise or fasting. I would be cautious about taking HMB before a critical race, as the breakdown of muscle may provide a valuable energy source.
=What is HMB?=
HMB, or "β-Hydroxy β-methylbutyric acid" to give it its full name<ref name="HMBPubChem"/>, is naturally produced in the body as the amino acid leucine is metabolized<ref name="MolfinoGioia2013"/>. It's been shown that leucine controls protein synthesis and metabolism<ref name="NortonLayman2006"/>, and it seems that one mechanism of action is via the HMB metabolite<ref name="NissenSharp1996"/>. My personal interpretation is that HMB tricks the body into acting as if it had consumed large quantities of protein, activating protein synthesis and inhibiting protein metabolism.
=HMB Benefits=
There are several benefits to HMB that make it of interest to runners.
* HMB inhibits muscle breakdown (proteolysis) after training<ref name="NissenSharp1996"/>, in old age<ref name="WuXia2015"/>, bed rest<ref name="DeutzPereira2013"/>, and muscle wasting conditions such as AIDS and cancer<ref name="Hasselgren2014"/>. Most importantly for athletes, HMB reduces muscle loss during calorie restricted training<ref name="ParkHenning2013"/>.
* HMB reduces muscle damage after endurance running (20Km/13 miles)<ref name="KnitterPanton2000"/>.
* HMB enhances the fat lose effects of exercise<ref name="StoutFukuda2015"/>.
* Not only does HMB reduce protein losses, it also increases protein synthesis, even in fasting subjects<ref name="WilkinsonHossain2013"/>. Subjects in that study were recreationally active, but not formally training. They did not perform heavy exercise for 72 hours and were overnight fasted. This is really interesting as it indicates that HMB can improve protein synthesis in the absence of recent exercise stress or protein intake.
* I found one study that showed two weeks of HMB reduce [[Lactate]] accumulation and increased VO<sub>2</sub> at 2 mM Lactate after <ref name="VukovichDreifort2001"/>. Personally, I suspect any improvement is probably due to changes in body composition.
* HMB may improve some markers of cardiovascular health, such as blood pressure and LDL cholesterol<ref name="NissenSharp2000"/>.
* There's some evidence from animal studies that HMB may reduce insulin resistance<ref name="SharawyEl-Awady2016"/><ref name="FuBruckbauer2015"/>, though in high doses (equivalent of >50g/day in humans) one study found increased insulin resistance<ref name="YonamineTeixeira2014"/>.
* HMB doesn't raise insulin levels<ref name="WilkinsonHossain2013"/>, unlike protein, so it doesn't inhibit fat loss (lipolysis.) This is critical given it's use to improve fat loss.
=How I take HMB =
This isn't medical advice, just my approach that you can use as a starting point. I'm continually tweaking my training and nutrition, so by the time I've finished writing this it's likely to be slightly different! My approach assumes I'm trying to reduce my body fat while keeping or increasing lean mass, which is fairly normal for me. The calcium form of HMB (the cheapest and most widely tested) peaks in the blood about 30 minutes after consumption<ref name="WilkinsonHossain2013"/>, and has a half-life of about 2.5hours<ref name="FullerSharp2010"/>. This means that timing seems to be pretty important.
* I don't follow the standard recommendation of 1g, 3 times per day. I did that initially, and I seem to have much better results by timing the doses more carefully based on the research. I'm also typically taking more than the 3g/day.
* I've found that intermittent fasting (IF) seems to work best for me to lose weight or just keep my weight under control. I often joke I have the genes of a natural athlete, but sadly my natural sport is sumo wrestling. I tend to use the 16:8 pattern of 16 hours of fasting and 8 hours of eating. However, this is a little modified depending on training. I typically break my fast mid-late morning.
* The combination of IF, HMB, high [[Protein]] intake and [[Vitamin C]] seems to work remarkably well for me. I aim for more than 3g/Kg of protein per day, which is on the high end of the recommendations for a calorie restricted athlete. I typically take 1-2g/day of Vitamin C, which seems to make a huge difference to my ability to adapt to endurance training. Without it, my ability to build up my distance seems seriously impaired.
* I usually take ~1g of HMB in a dose, either mixed in a calorie free electrolyte drink or in a protein smoothie. The taste is a little musty but not unpleasant to me. I've had no GI issues with HMB, nor heard of any being reported.
* On rest days, I'll take HMB while fasting, often with some Vitamin C. I aim to take HMB about every 3-5 hour to push my body towards burning body fat rather than muscle. While I'd like to think the HMB will actually build muscle, I suspect that being fasted and calorie restricted makes this unlikely at this point in my day.
* I break my fast on rest days with Casein protein with HMB and Vitamin C. The idea here is to provide protein without raising insulin too much. I'm hopeful that I can extend the fat burning into this early part of the post-fast. Casein has a lower insulin response than whey<ref name="ReitelsederAgergaard2011"/>. That study showed casein resulted in a lower insulin response from 15 to 60 minutes, a peak insulin of ~110 v 180 for whey (pmol/L), and with a total insulin response (area under the curve) of 15.6 v 18.5 for whey.
* On rest days I will often do a brief [[High Intensity Interval Training]] session on the bike trainer. This is typically 4-6x 12 seconds at 7-9 watts/Kg with 2-minute recoveries. I mostly time the session around the HMB intake.
* On training days, I often will take HMB, with ~5g of Arginine, ~5g of Citrulline-Malate, and 6-8oz beetroot juice just before starting running. The goal of the other ingredients is to boost blood supply to the muscles.
* My nutrition during the run varies, but typically I refuel every 60-120 minutes. Sometimes my "fuel" will be just an HMB/Vitamin C dose in an electrolyte drink, but doing a marathon+ length training run without calories is tough. I'll often take 5-10g of whey protein as fuel, which makes a huge difference (possibly placebo) to my performance. If I'm feeling the need, often on back to back marathon+ days I'll add 5-10g sugar to the mix. My aim is to stay in sufficient calorie deficit that I can convince myself I'm still fasting.
* What I do at the end of the run depends on timing. If I'm ready to end the fast, I'll typically make a hot chocolate with 1 tablespoon pure cocoa, 25g whey, and 8oz of milk. If the fast is continuing then it will just be HMB and vitamin C.
* I finish my eating period with Casein protein, milk, and sometimes eggs, but without HMB. My goal is to have a supply of protein available for the early part of the fast, including the initial sleep period.
* I take an HMB & Vitamin C dose just before sleeping, typically 1-3 hours after starting the fast. This is to keep the HMB levels up overnight to prevent muscle metabolism.
* Depending on how I'm feeling, I sometimes take a dose of HMB in the middle of the night.
=HMB Forms=
HMB is available as a calcium salt or as a free acid, with the free acid resulting in a more rapid rise in blood HMB levels, has nearly twice the area under the curve, and has 25% greater utilization<ref name="FullerSharp2010"/>. The free acid has a half life of ~3 hours and the calcium salt is ~2.5 hours<ref name="FullerSharp2010"/>. However, most research has been on the calcium salt, and the free acid form is more expensive, so personally I've only used the calcium salt.
/
A comparison of Calcium (open circles) with oral free acid (solid circles), and sublingual free acid (triangles) of HMB.
=HMB Safety=
Since it's first use as a nutritional supplement in 1997, HMB has been extensively studied, and found to be safe in both human and rodents<ref name="WilsonFitschen2013"/>. There was one study that found high doses of HMB, the equivalent of over 50g/day in humans, increased insulin resistance<ref name="YonamineTeixeira2014"/>, though other studies show improved insulin resistance at typical levels (see above). However, contamination of supplements is an issue, with at least one athlete testing positive due to taking an HMB supplement<ref name="wada"/>.
=References=
<references>
<ref name="wada">wada-ama.org !!work!!, 6 December 2019 !!access-date!!, https://www.wada-ama.org/sites/default/files/resources/files/cas_2008_a_1510_despres.pdf</ref>
<ref name="StoutFukuda2015">Jeffrey R. Stout, David H. Fukuda, Kristina L. Kendall, Abbie E. Smith-Ryan, Jordan R. Moon, Jay R. Hoffman, β-Hydroxy-β-methylbutyrate (HMB) supplementation and resistance exercise significantly reduce abdominal adiposity in healthy elderly men, Experimental Gerontology, volume 64, 2015, pages 33–34, ISSN [http://www.worldcat.org/issn/05315565 05315565], doi [http://dx.doi.org/10.1016/j.exger.2015.02.012 10.1016/j.exger.2015.02.012]</ref>
<ref name="NortonLayman2006">Layne E. Norton, Donald K. Layman, Leucine Regulates Translation Initiation of Protein Synthesis in Skeletal Muscle after Exercise, The Journal of Nutrition, volume 136, issue 2, 2006, pages 533S–537S, ISSN [http://www.worldcat.org/issn/0022-3166 0022-3166], doi [http://dx.doi.org/10.1093/jn/136.2.533S 10.1093/jn/136.2.533S]</ref>
<ref name="FullerSharp2010">John C. Fuller, Rick L. Sharp, Hector F. Angus, Shawn M. Baier, John A. Rathmacher, Free acid gel form of β-hydroxy-β-methylbutyrate (HMB) improves HMB clearance from plasma in human subjects compared with the calcium HMB salt, British Journal of Nutrition, volume 105, issue 3, 2010, pages 367–372, ISSN [http://www.worldcat.org/issn/0007-1145 0007-1145], doi [http://dx.doi.org/10.1017/S0007114510003582 10.1017/S0007114510003582]</ref>
<ref name="MolfinoGioia2013">Alessio Molfino, Gianfranco Gioia, Filippo Rossi Fanelli, Maurizio Muscaritoli, Beta-hydroxy-beta-methylbutyrate supplementation in health and disease: a systematic review of randomized trials, Amino Acids, volume 45, issue 6, 2013, pages 1273–1292, ISSN [http://www.worldcat.org/issn/0939-4451 0939-4451], doi [http://dx.doi.org/10.1007/s00726-013-1592-z 10.1007/s00726-013-1592-z]</ref>
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