How Much Does Weight Actually Matter In Running?

インデックス作成: 2026-05-22

[00:00:00]How much faster can you actually run for every pound you lose? The truth is, most runners are chasing the wrong number.

[00:00:07]But after working with thousands of runners and going through the research, I found what actually matters. So, in this video, I'm going to show you exactly how much weight affects your pace, what the research actually says, and the three factors that matters more than the number on the scale. So, first things first, how much faster can you actually get if you lose a pound of body weight? Most people in the running community will tell you about 1 second faster per 1 pound of body weight lost.

[00:00:37]And this idea is based on a study from 1978 that showed that for every extra pound you're carrying, you slow down by about 1.4 seconds per mile. But, here's the thing, getting leaner isn't always the same as getting faster, and most runners actually mess this up. Let me show you why. So, in 2007, researchers found that just supporting your body weight can take up to 74% of your running energy. But, it's not just about how much weight you're carrying, it's where you're carrying it that matters most. Because studies have shown that if you have more weight in your legs compared to your trunk, you'll actually run slower. But, if that same weight sits in your trunk instead, you'll run faster. So, why does this happen? It happens because the further weight is from your center of mass, the more energy your muscles need to swing, lift, and stabilize with every single stride.

[00:01:38]And that's what's known as the lever principle. It's why elite runners obsess over every single gram on their feet in a way they just don't about their torso.

[00:01:48]So, knowing this, what can you actually do about it? Now, losing body fat does help, but the easiest place to start is the weight of your gear. Your shoes, your socks, and even your watch matters a lot. And it's simply because a gram saved on your feet or your wrists cost you far more energy over a mile than a gram saved anywhere else. But what matters most then? Your fitness or your weight?

[00:02:18]Let me show you so you don't waste your time on the wrong thing. So, here's the thing. Most runners think that if you're just light enough, you'll be fast enough. But when I went through the research, I kept finding something that didn't quite add up. Heavier runners were sometimes outperforming lighter ones. Let me show you why. So, a study on ultra runners found that heavier runners could run as fast and sometimes faster than lighter ones. And not because weight doesn't matter, because it does. You would think it especially matters in an ultra marathon where you're carrying that weight for hours.

[00:02:59]But what the heavier runners had done was to find a way to compensate for it.

[00:03:04]Because even though everyone racing is in peak shape, the heavier runners often had better overall fitness. This means that the disadvantage of weighing more is real, but it's not equal to worse performance. It can be outworked with different strategies. And during my professional triathlon career, I saw this in practice. I trained with a guy who could run a 5K in 15 minutes and 30 seconds at 95 kg. Now, here's what that means for you. If you're carrying a bit more weight than you'd like, then don't focus all your energy on losing it.

[00:03:46]Focus on getting faster instead because most of the time training harder will lead to weight loss anyway. And even if it doesn't, it's not necessarily a problem if you're still getting faster.

[00:04:00]But, this is where a lot of runners go wrong because there's one thing that ruins performance when it comes to weight more than anything else. And unfortunately, it's very common and it's quite dangerous. So, let me show you how to avoid it. So, here's the thing. When most people get into running and start training more, the first instinct is usually to get as light as possible as fast as possible. But, that's probably the worst thing you can do. Let me show you why. So, imagine you're trying to keep a fire burning. But, instead of adding wood, you start taking one piece away every 10 minutes or so. At first, it seems fine. But, slowly the flame gets smaller and smaller until eventually it goes out. That's exactly what happens when you're training hard but not eating enough. Your body starts rationing everything it has. So, your immune system weakens, your recovery falls apart, and your performance goes with it. And this problem is so common in running that it actually has a name.

[00:05:10]It's called RED-S and it stands for relative energy deficiency in sports.

[00:05:16]It's so common because it's counterintuitive.

[00:05:19]You think that eating less and losing weight would make you faster. But, when you're training hard, it will actually make you worse. So, here's what I want you to take away from this. Stop measuring your progress on the scale and start measuring it in your performance instead. If you're getting faster and running further week by week, you're doing just fine. And if you do want to lose some weight, save it for when your training load is lighter, so your body actually has the energy to do it properly. But, here's what most runners never figure out. The lightest person on the start line doesn't always win, and there's a specific reason why.

[00:06:03]Let me show you what it is. Most runners think that the only way to run faster is to either train harder or get lighter.

[00:06:11]But, there's a third option, and it might be the most effective of the three. Let me show you what I mean. So, imagine your body is a smartphone. An older model and a newer model can be exactly the same size and weight, but the newer one runs faster because the processor inside it is more powerful.

[00:06:31]Your body works the same way. The number on the scale is just the size of the phone.

[00:06:38]What actually determines your performance is the processor, meaning how much force your muscles can produce with every step. This is called the power-to-weight ratio, and multiple scientific reviews have found that adding strength training improves running economy by 2 to 4% without you having to gain or lose a single pound.

[00:07:02]Simply by upgrading your processor. So, instead of always chasing a lighter body, start chasing a more powerful one.

[00:07:12]Add strength training or hill sprints to your weekly schedule. You're not just trying to change the size of the phone.

[00:07:19]You're upgrading what's running inside it. So, now you know how much weight actually matters and what to do about it. But, if you're not training the right way, then it doesn't matter anyway. So, go watch this video next.

[00:07:34]Well, I'll show you how to run so fast that it feels illegal.