The World's Fastest Workout for Fat Loss

by Mike T Nelson, PhD

230 Seconds to Leanness

The fastest workout will give you results in just 30 seconds. How's that possible? It has to do with leptin. Here's why and how to do it.

Leptin And The World’s Fastest Workout

The body isn’t a simple, linear, or straightforward machine – it’s complex. And overcomplicating the fat-loss process usually backfires. But just because the physiology is messy doesn’t mean your actions can’t be simple and effective.

Understanding the hormone leptin may help uncover the answers to getting leaner. The good news? Making this hormone work for you instead of against you only takes 30-seconds a day… 30 very INTENSE seconds.

First, here’s a short crash course on leptin.

What Is Leptin Anyway?


Leptin was discovered by researchers in the '50s. Fast forward to the '90s when it was “rediscovered,” and many predicted it would be the biggest weight loss breakthrough ever.

It’s a hormone that’s released primarily by fat cells (adipocytes) and works to regulate appetite, body fat mass, and basal metabolic rate. Until just a few years ago, researchers thought fat cells were just storage facility for unsightly body fat. We know now that they’re very metabolically active, releasing and receiving a myriad of messenger hormones, one of which is leptin.

Leptin travels up to the brain where it acts on receptors in the hypothalamus to inhibit appetite. More leptin in your brain = less food intake.

This is great news for anyone looking to get leaner since more leptin means you’ll be less likely to overeat. Leptin is your body’s way of putting the brakes on fat gain by decreasing appetite.

The chronic level of leptin you have is also a rough measure of the amount of fat you have on your body. Many things can affect leptin:

Factors Promoting Leptin Secretion

  • Excess energy stored as fat (obesity)
  • Overfeeding
  • Glucose
  • Insulin
  • Glucocorticoids
  • Estrogens
  • Inflammatory cytokines, including tumor necrosis factor and Interleukin-6 (acute effect)

Factors Inhibiting Leptin Secretion

  • Fasting
  • Catecholamines and adrenergic agonists
  • Thyroid hormones
  • Androgens
  • Low energy states with decreased fat stores (leanness)
  • Peroxisome proliferator–activated receptor-agonists
  • Inflammatory cytokines, including tumor necrosis factor (prolonged effect)

How Obese Mice Got Sexy Fast


Researchers in the '90s did a series of mouse experiments to show that mice with messed-up leptin became profoundly obese. Their metabolic rate was lower, they didn’t move as much, and they ate tons of food.

The mice didn’t make any leptin at all. To make the mice lean, they injected it with leptin, and voila – thin mice again!

The researchers thought this was the solution to the obesity problems: just inject humans with leptin and poof, thin humans. The problem is, it didn’t work. Researchers measured blood levels of leptin in obese humans and found that their leptin levels were sky high!

That wasn’t supposed to happen. Leptin levels were expected to be low since the humans were fat. As leptin increases, it tells the brain that the body has enough fat. So you see why they would expect low leptin levels in obese populations.

Remember, when injected with leptin (thus increasing the level), the mice in the studies got thinner. But the obese humans already had high levels of leptin. Injecting more leptin was like pissing in the ocean to try to raise the water level.

What researchers discovered was that the receptor for leptin may be what’s out of whack in the obese. The receptor isn’t telling the brain that leptin is high. They may have tons of leptin, but the brain can’t tell since the receptor is broken. So the answer for leanness isn’t about increasing leptin but increasing the body’s sensitivity to it.

Exercise That Increases Leptin Signaling

Sprint training is a great way to burn fat, but it may have another benefit. Researchers in 2011 looked at sprints as a leptin-signaling mimetic.

This study used a group of fit people who were pretty lean (about 15% body fat) and young (23 years old). They split them into two groups: a fasting group, and a glucose group which ingested 75 grams of glucose an hour before sprints.

Both groups did one Wingate bike sprint for only 30 seconds. If you’re not familiar with this setup: you hop on a bike with the resistance set to a high workload (10% of body weight used here) and pedal like a rabid grizzly bear is chasing you.

Subjects had a series of muscle biopsies done throughout the study, and researchers found that a single session of sprint training showed alterations in leptin signaling.

The sprints were jacking up leptin that, in theory, should cause obese to start dropping fat. However, this wasn’t seen in the group that ingested glucose before their sprint. Only the fasted group saw leptin alterations. It appears insulin may interfere with leptin signaling to some degree.

The researchers said that sprints done while fasting elicited signaling like what was found in the rodents’ muscle after receiving leptin injections. But glucose ingestion before the exercise diminished the effect.

So it appears that fasted sprint training can pinch hit for leptin and sensitivity to it.

Sample Sprint Workout

Want to give this a shot? Get on a bike and work up to a single, maximum, pedal-as-hard-as-you-can sprint for 30 seconds.

The tension should be relatively high, but the goal is to keep your pedaling at a fast pace for the entire 30 seconds. If you slowed to a snail’s pace 20 seconds in, go to a lighter workload. Do this fasted, like first thing in the morning.

Don’t have a bike? While the study didn’t look at running, it may elicit the same response because the pathways are very similar.

It sounds ridiculously simple, but my experience with my athletes shows that this does seem to help speed fat loss.

Sum It Up For Me!

  • More leptin production is associated with less food intake, but only in those whose body responds to leptin properly.
  • Some may have a leptin receptor issue where it’s not responding to the amount of leptin floating around.
  • Science isn’t at the point yet where we can always tell who has a receptor issue, but the more overweight you are, the more likely you have broken leptin receptors.
  • Doing just one sprint in a fasted state works to pinch hit for leptin, putting you on the road to leanness. Non-fasted training doesn’t have the same effect.
  • Fasted sprints can be done any time on a fasting day or done before breakfast. This way, it’s unlikely to interfere with your normal training session.




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  3. Galgani JE et al. Leptin replacement prevents weight loss-induced metabolic adaptation in congenital leptin-deficient patients. J Clin Endocrinol Metab. 2010 Feb;95(2):851–855. PMC.
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Gonna give this a try in the mornings and see if I notice that I’m less hungry and eat less food. Got a Rogue Echo Bike in the garage, and 30s sprinting on that thing is definitely intense enough…so good it’s bad lol


Strange. Andrew Huberman just spoke about this in his suggestions for fat burning.

Get up and run like someone is chasing you, do not eat until 2pm, quit alcohol. I’m about to head out and do some sprints


Does this, then, in a fashion, reinstate the long held belief that fasted cardio is superior? Albeit, the cardio is now a sprint, but it would seem there is some truth to the old ways. Like a previous article pointed out sometimes scientific analysis gets in the way of actual real world proof.

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That’s exactly what I was wondering! But so many fitness experts have told us over the past few years that fasted cardio does nothing for fat loss because it doesn’t have much of an impact on caloric expenditure.

To them the only thing that matters is CICO (calories in calories out). But they’re not considering all the indirect pathways that promote fat loss, like becoming more leptin sensitive.

So, good question and thank you for asking it! I don’t have the answer, but glad to know we’re on the same page.

I’d say… not quite. Mainly because this method (a single 30-second fasted sprint) isn’t what most people are thinking when they think “cardio.” It’s not really cardio, which is basically getting your heart rate up and keeping it up for a prolonged period of time. This is a different thing.

In the studies we’ve written about, most compared a standard cardio session done fed to a standard cardio session done fasted. Both types of cardio workouts were the same: duration, intensity, etc.

As I recall, doing fasted cardio might lead to 2 extra pounds of fat loss over a 6-month period versus fed cardio of the same type for the same time period. And that’s being generous with the math. (But maybe that’s worth it for some people?)

But that doesn’t account for the possible monkey wrenches: muscle loss, elevated cortisol, etc. Steroid-using coaches and bodybuilders were all over fasted cardio, but the drugs made those possible issues moot, as bodybuilding drugs tend to do.

Also, 2 possible pounds of extra fat loss in 6 months can be achieved in ways that don’t involve early morning fasted cardio, like… eating one less bite of food every night at dinner, having one beer instead of three on the weekend, etc. In other words, some pretty minor diet changes.

So, am I crapping on this 30-second sprint method? Not at all! I think it’s smart and it works. Just pointing out that this isn’t “cardio” in the traditional sense of the word; it just looks like it. It’s more of a leptin hack. At the very least, it’s a nice form of “exercise snacking.”

Here’s some more info:

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Interesting. I recall an article from TC, I believe, about brown fat cells (that’s a wild guess) being more stimulated with fasted cardio. In any event, I’ve always used cardio more for heart health (and playing with my dog) rather than fat loss, which is like Sisyphus and his rock.


Agreed. Any other benefit is just a nice bonus. Also, traditional cardio or metcon is where you can have FUN in the gym and use a lot of variety. After all, the goal is to NOT adapt to it.

I haven’t done this in a while, but my favorite cardio method used to be “20 Minutes of Anything.” Set a timer and just keep sucking air until it beeps. (I know, the smart watch wearers, over-analyzers, and number-obsessives are having fit right now.) So that might be 5 minutes on a stairmill, 5 minutes of light KB swings, 5 minutes of battle ropes, and 5 minutes of hopping while listening to “Jump Around” by House of Pain. Doesn’t matter. As long as it sucks.

"But I ain’t going out like no punk bitch
Get used to one style and yo and I might switch…"



Would it be considered a 'fasted state" if I were drinking my own concoction of D-ribose/peptopro/electrolyte?

@Chris_Shugart did you seriously post right after your wife to disagree with her? I see you’re taking the “run like someone is chasing you” seriously.

I totally get the points on whether 2 lbs in 6 months is negligible. I think in two situations it’s totally worth it:

  1. Why not? If it’s no additional sacrifice to me (I don’t care when I do cardio), why wouldn’t I get the most out of it I could?
  2. Competition. If I’m going to get on stage, and I’m already down to minimum bites at dinner, I’m taking every possible advantage.

Neither of those apply to me, or probably most of us, so we just do our extra 30 seconds or whatever it amounts to!

I also really like the point about cardio is… cardiovascular training! It’s not a great tool for fat loss anyway, which definitely had me ignore it for years because I looked at it the wrong way. I could get lean with very little cardio and more efficiently by being strict with my diet, and I hated doing any cardio, so I just didn’t. It wasn’t until I got old enough that health markers actually popped up that I changed my thinking.

I think this is where we get into the silly conversations you point out (if I do it this way, will I lose another pound). It’s somewhat akin to asking which screwdriver handle gives you the best chance to pound nails: you can certainly make some arguments for one, but that’s still not the point.

Anyway, 90% of this was just me trying to dig out from the opening salvo.

  1. If your diet is good (caloric intake and nutritional choices both), does it still work?
  2. I would consider myself skinny fat, due to poor appetite and not eating enough calories. Would this exercise still work for me? Is my leptin high or low or are my leptin receptors malfunctioning?

Interesting. This seems could be the reason why ketogenic diets are more apetite suppressing.

OK, this is interesting, but one thing…

I am much older, and nowhere near 15% and just recently started something somewhat similar.
No I didn’t go all out for 30 seconds. What I did do was “warm up” for a minute, at the top of the 1st minute, I started to accelerate, watching the RPMs, pushing until I couldn’t increase RPMs. It really only took about 10 seconds. I eased back a ton, under 60RPM until the timer says :30 and did it again. Don’t do anything until the timer says 3:00, and repeat. Like 3:00-3:10, 3:30 -3:40, 5:00 - 5:10, 5:30 - 5:40…
at this point I don’t get near the RPMs as I did at 1:00 and 1:30, so I’m done. I do pedal slowly @ < 60RPM until my heart rate drops to 115.
I am doing it fasted.
I haven’t been as consistent as I’d like. I should do it every other day. If a gym day on a recumbent bike at the gym or if not, on my echo.

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This is great. 30 seconds of hell? I know Tabata was hard but I’ll trust you guys and do it. I can torture myself for 30

Dr Mercola has this Sprint 8 elliptical workout that sounds up your alley. Warmup, 30 seconds all out, 90 seconds easy, repeat 7 more times

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I dropped 8 points off bf mid May to mid June and this perfectly explains the science behind it all. 20-25 seconds @12-14 on treadmill with 1.5 incline. Great for lifting endurance and fast twitch quad fibers!

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Love this article. Fasted Cardio is one of those things I do and I absolutely believe it is more fat burning than non-fasted. I have read much of the research pro and con and I am staying with my personal experience - Fasted Cardio burns more fat and is more effective at weight loss and appetite suppression. May not be true for others but it damn sure is for me. This leptin thing may be part of it, I do not know but for me personal experience trumps lab results.

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