Doug, a reader of this newsletter, recently asked:

Doug’s question taps into a major debate in fitness: Is high-intensity work really better for fat loss than steady-state cardio like walking?

My answer would have been no after a conversation with an expert a few months back as to why so many see no results after months at these cycling and intense work out classes. But there may be more to that down below. 🙂 

I also thought about “burning fat”—as if fat were flammable, destroyed by heat. But is that how it really works? Does getting extremely hot (like sitting in a sauna) burn fat? Do people living in hotter climates burn more fat naturally?

Here’s what the science actually shows—and how you can apply it for real fat loss.

✅ What HIIT Does Well

High-Intensity Interval Training (HIIT)—short bursts of all-out effort followed by rest—burns fat very efficiently, thanks to several key mechanisms:

• Post-Exercise Calorie Burn: HIIT significantly increases Excess Post-Exercise Oxygen Consumption (EPOC), meaning your body continues burning calories for hours after your workout ends [¹].

• Improved Insulin Sensitivity: HIIT enhances your cells’ responsiveness to insulin, reducing the risk of storing visceral fat—the deep, dangerous fat around your organs [²].

• Targeting Visceral Fat: Studies show HIIT reduces visceral fat more effectively than moderate-intensity continuous exercise, even when overall body weight doesn’t change [³].

• Time Efficiency: A 15-minute HIIT session can deliver similar or superior fat loss benefits compared to 45 minutes of steady-state exercise like jogging [⁴].

Doug, your instincts are right and mine were wrong(ish)—short, intense intervals can be a very potent tool for burning visceral fat and improving metabolic health.

❌ What HIIT Doesn’t Do

However, it’s crucial to debunk a persistent myth:

• You Can’t Spot Reduce: No matter how hard you sprint or how many sit-ups you do, you cannot selectively burn fat from your belly. Fat loss occurs systemically, influenced by overall metabolic demand and hormonal signals [⁵].

• Visceral Fat Goes First (Usually): Improving metabolic health (which HIIT does well) often triggers visceral fat loss early, but it’s not “targeted” in the way many hope.

🚶‍♂️ How Walking (Zone 2 Training) Compares

I’m a huge fan of walking for so many reasons - you’re getting sunshine, fresh air, in nature and all the benefits that come with that and time to think.

But, what about walking or steady-state cardio (Zone 2 training) for fat burning?

Zone 2 refers to exercising at a low-to-moderate intensity where your body primarily burns fat as a fuel source [⁶]. Benefits include:

• Direct Fat Oxidation: At lower intensities, the body uses a higher percentage of fat for energy compared to carbohydrates [⁶].

• Low Stress, Sustainable: Zone 2 cardio doesn’t stress the body nearly as much as HIIT, making it ideal for daily, long-term practice [⁷].

• Improved Mitochondrial Function: Regular steady-state training enhances your cells’ ability to burn fat by improving mitochondrial health [⁸].

But: While Zone 2 burns a higher percentage of fat during exercise, it doesn’t create the same EPOC effect after exercise. It also tends to burn fewer total calories unless done for long durations.

🧠 How to Integrate Both for Best Results

If you’re over 40 (yes I am) and want a sustainable fat-loss plan, combine both:

• 2 HIIT sessions per week: 10–15 minutes, e.g., 20-second sprints + 1-minute recovery x 6 rounds.

• Daily Zone 2 walks: 30–60 minutes at a conversational pace.

• Recovery Focus: Allow at least 48 hours between HIIT sessions to let your nervous system and muscles recover fully.

This blend gives you the fat-burning power of HIIT and the low-stress, metabolic benefits of steady-state walking.

🧪 Bottom Line

• HIIT is highly effective for improving insulin sensitivity, shrinking visceral fat, and triggering long-term fat-burning metabolism.

• Zone 2 training burns fat during exercise and is sustainable for everyday health and fat loss.

• Doug’s hunch was right: Max-effort intervals are a scientifically supported fat-loss accelerator—but combining them with daily walking provides the best overall strategy.

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Any topic you’d like me to research and cover? 👋

I write this newsletter each week because I feel my best when my body, mind and soul are all healthy. I want the same for you. If you feel like you’ve seen something valuable here, please do me a favor and forward this newsletter to a friend or let me know what you think by replying or texting me - (310) 879-8441

I think the world is in desperate need of healthy, happy men who love the strong women in their lives with a self-sacrificing type of love.

I have found the following four books to be the 4 books every man should read and every woman should want their man to read.

• Good Energy - What makes for a Healthy Body and Mind?

• The Masculine in Relationship - How to Win the Trust, Lust and Devotion of a Strong Woman

• The Man’s Guide to Women - The Science of Happy Relationships

• The Desire of Ages - Leadership in a World of Cowards

Here are a few other links to things that have changed my life:

Whoop - Track your HRV and REM Sleep

Function Health - Optimize Your Health via 100+ BioMarkers

Here are a few topics I think you’ll love if you haven’t checked them out before:

How to Breathe for Better Health

How to Supercharge Your Sleep

The Power of the Sauna

-Jared

P.S. - This newsletter does not provide medical advice. The content, such as graphics, images, text, and all other materials, is provided for reference and educational purposes only. The content is not meant to be complete or exhaustive or to be applicable to any specific individual's medical condition.

References

1. LaForgia J, Withers RT, Gore CJ. Effects of exercise intensity and duration on the excess post-exercise oxygen consumption. Journal of Sports Sciences. 2006;24(12):1247–1264.

2. Boutcher SH. High-intensity intermittent exercise and fat loss. Journal of Obesity. 2011;2011:868305.

3. Maillard F, Rousset S, Pereira B, et al. High-intensity interval training reduces visceral fat more effectively than moderate-intensity continuous training. Obesity Reviews. 2018;19(2):265–278.

4. Gibala MJ, Little JP, van Essen M, et al. Short-term sprint interval versus traditional endurance training: similar initial adaptations in human skeletal muscle and exercise performance. Journal of Physiology. 2006;575(3):901–911.

5. Stallknecht B, Dela F, Helge JW. Are fat oxidation rates higher during exercise in abdominal obesity? American Journal of Physiology-Endocrinology and Metabolism. 2007;292(1):E24–E28.

6. Achten J, Jeukendrup AE. Optimizing fat oxidation through exercise and diet. Nutrition. 2004;20(7–8):716–727.

7. Seiler S. What is Best Practice for Training Intensity and Duration Distribution in Endurance Athletes? International Journal of Sports Physiology and Performance. 2010;5(3):276–291.

8. Bishop DJ, Granata C, Eynon N. Can we optimize the exercise training prescription to maximize improvements in mitochondria function and content? Biochimica et Biophysica Acta (BBA) - General Subjects. 2014;1840(4):1266–1275.