HMB For Runners
HMB is a supplement that may help preserve muscle during weight loss, something that is typically quite difficult. It may also be valuable for those who struggle to maintain weight during heavy training. 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.
1 What is HMB?
HMB, or "β-Hydroxy β-methylbutyric acid" to give it its full name, is naturally produced in the body as the amino acid leucine is metabolized. It's been shown that leucine controls protein synthesis and metabolism, and it seems that one mechanism of action is via the HMB metabolite. 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.
2 HMB Benefits
There are several benefits to HMB that make it of interest to runners.
- HMB inhibits muscle breakdown (proteolysis) after training, in old age, bed rest, and muscle wasting conditions such as AIDS and cancer. Most importantly for athletes, HMB reduces muscle loss during calorie restricted training.
- HMB reduces muscle damage after endurance running (20Km/13 miles).
- HMB enhances the fat lose effects of exercise. There is some evidence that HMB directly increases fat loss (lipolysis), though the only reference I could find to this is in a patent.
- Not only does HMB reduce protein losses, it also increases protein synthesis, even in fasting subjects. 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.
- HMB may improve some markers of cardiovascular health, such as blood pressure and LDL cholesterol.
- There's some evidence from animal studies that HMB may reduce insulin resistance, though in high doses (equivalent of >50g/day in humans) one study found increased insulin resistance.
- HMB doesn't raise insulin levels, unlike protein, so it doesn't inhibit fat loss (lipolysis.) This is critical given its use to improve fat loss.
- I found one study that showed two weeks of HMB reduce Lactate accumulation and increased VO2 at 2 mM Lactate after . Personally, I suspect any improvement is probably due to changes in body composition.
- The commonly used dose of HMB is 1g given 3 times a day. I could find no research that established this is the right dose as few studies compare multiple levels.
- HMB may improve wound healing, though I only found one study that used HMB and two amino acids (arginine & glutamine) on elderly subjects.
- I expected HMB to improve tendon healing, but I found no research in this area. There is a patent for using HMB to improve tendon healing, but it's based on case studies only.
- HMB is surprisingly cheap; buying in bulk from amazon.com (see below) costs less than $0.10 per dose (1 gram.)
3 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. If you're one of the athletes who has trouble maintaining or gaining weight then your approach is likely different. The calcium form of HMB (the cheapest and most widely tested) peaks in the blood about 30 minutes after consumption, and has a half-life of about 2.5hours. 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. (See "Casein or Whey?" below.)
- 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.
- Excluding the start and end of the fast I aim to eat a variety of foods that are nutrient dense, focusing on vegetables and fruit, along with dairy and eggs. I have a very low meat intake, generally once a week or so.
- 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. (Protein intake before sleep has been shown to increase muscle protein synthesis.)
- 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.
4 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. The free acid has a half life of ~3 hours and the calcium salt is ~2.5 hours. 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.
5 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. There was one study that found high doses of HMB, the equivalent of over 50g/day in humans, increased insulin resistance, 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.
6 Casein or Whey?
On a related topic, should you use whey or casein protein? (I'll ignore other types of protein for now.) I'd like to think that using Casein can extend the fat burning into this early part of the post-fast, but I'm not sure the research supports my optimism. Certainly, casein has a lower insulin response than whey. That study compared 0.3 g/kg lean body mass of whey or casein in healthy subjects (that's just ~17g.) The casein resulted in a lower insulin response from 15 to 60 minutes, with a peak insulin of ~110 (casein) v 180 (whey), both pmol/L. The total insulin response (area under the curve) was 15.6 for casein v 18.5 for whey. It's not clear that the difference would change the impact on fat burning (lipolysis.) It only requires 12 pmol/L of insulin to suppress 50% of lipolysis, 22 pmol/L to suppress 70%, and 34 pmol/L to suppress 90%. This suggests that the difference between casein and whey isn't going to impact lipolysis.
For a sense of how insulin changes during exercise, a study of trained cyclists exercising while fasted at 74% V̇O2max for 2 hours found their insulin levels dropped from 14.3 to 10.7 pmol/L after 30 minutes then remained around 8-6-9.7 pmol/L. When given carbohydrate at 1.0g/Kg at the start, then 0.25g/Kg at 60 and 90 minutes, their insulin remained around 13-15 pmol/L. (1.0 g/Kg was ~70g or 280 Calories, 0.5 g/Kg was ~17g or 70 Calories for the subjects.)
7 Support This Site
This is the HMB powder I use; it's the calcium form, which is much cheaper and more widely studied than the free acid.
This review was made possible by readers like you buying products via my links. I buy all the products I review through normal retail channels, which allows me to create unbiased reviews free from the influence of reciprocity, or the need to keep vendors happy. It also ensures I don't get "reviewer specials" that are better than the retail versions.
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