Key Takeaway
The "best" cardio for you depends on your goals, fitness level, and what you'll actually stick to. Both HIIT and LISS are valuable tools, but neither is inherently superior for fat loss. Total calorie deficit matters more than cardio type.
Listen, I get it. You're wondering whether to sprint like your life depends on it or cruise along at a comfortable pace while watching Netflix. The internet gives mixed messages — "HIIT is the key to fat loss!" vs "Steady-state is the way!" Well, I've tried both extremes for years until I finally studied the research and found out what actually works.
Here's the truth: HIIT and LISS each have their place, but the "best" for you depends on your goals, fitness level, and what you'll actually commit to. Let me break down what the science really says, without the hype.
What Exactly Are We Comparing?
HIIT (High-Intensity Interval Training)
Alternating between brief bursts of maximum effort and recovery periods. Think 30 seconds of all-out sprinting, then 90 seconds of walking. Total workout duration: usually 15-25 minutes.
Traditional HIIT Protocol:
- Warm-up: 5 minutes
- Work interval: 30-60 seconds at 85-95% max heart rate
- Recovery interval: 60-120 seconds at 50-65% max heart rate
- Repeat: 6-10 repetitions
- Cool-down: 5 minutes
LISS (Low-Intensity Steady State)
Maintaining a steady, comfortable pace for an extended period. Like a brisk walk, easy bike ride, or that "I could do this while having a conversation" jog. Usually 30-60 minutes at 50-65% of your max heart rate.
The Calorie Burning Truth
Here's where people get confused. Yes, HIIT burns more calories per minute. But LISS sessions are typically longer, so let's look at the actual numbers:
During Exercise:
- HIIT (20 minutes): 200-300 calories
- LISS (45 minutes): 250-400 calories
The EPOC Effect (Afterburn):
This is HIIT's secret weapon. Excess Post-Exercise Oxygen Consumption keeps you burning calories after your workout ends. HIIT can increase your metabolism for 14-48 hours post-exercise, burning an additional 50-200 calories.
Reality check: That afterburn effect everyone hypes? It's maybe 6-15% of calories burned during the workout. Nice bonus, but not the game-changer Instagram makes it out to be.
What The Research Actually Shows
Fat Loss Studies
A 2017 meta-analysis of 28 studies found that both HIIT and moderate-intensity continuous training produced comparable fat loss when calorie expenditure was matched.
Translation: It comes down to total calories burned, not cardio type.
The Interference Effect
Here's something crucial if you lift weights: too much HIIT can interfere with muscle and strength gains compared to LISS. A 2012 study found that those doing high-intensity cardio showed reduced strength gains compared to those doing lower-intensity cardio.
Personal note: I learned this the hard way. Doing HIIT 4 times a week while trying to build muscle is like driving with the parking brake on.
Which Burns More Fat?
The million-dollar question. With LISS, you burn more calories from fat (around 50-65%). With HIIT, it's mostly carbs fueling the effort. But here's the catch — it doesn't matter.
Why? You lose fat when you're in a caloric deficit over time. Your body will tap into fat reserves to balance the energy deficit regardless of what fuel you used during exercise.
Think about it: whether you pay for gas with cash or credit card, your bank account still decreases by the same amount at the end of the month.
The Real Pros and Cons
HIIT Benefits:
- ✓ Time-efficient (15-25 minutes)
- ✓ Improves VO2 max better
- ✓ Can be less boring/more engaging
- ✓ Small metabolic boost after exercise
- ✓ Improves insulin sensitivity
HIIT Drawbacks:
- ✗ Higher risk of injury
- ✗ More stressful to the body (more cortisol)
- ✗ Harder to recover from
- ✗ May disrupt strength training
- ✗ Not recommended for beginners
LISS Benefits:
- ✓ Lower risk of injury
- ✓ Can be done daily
- ✓ Less stressful on joints
- ✓ Promotes recovery
- ✓ Can be done socially
- ✓ Builds aerobic base
LISS Drawbacks:
- ✗ Time-consuming (45-60+ minutes)
- ✗ Can be boring
- ✗ Less sport performance improvement
- ✗ Adaptive thermogenesis if done excessively
My Personal Protocol (What Really Works)
After years of trial and error, and studying research, here's what I've found works best for most people:
For Fat Loss While Maintaining Muscle:
- 2x HIIT weekly (20 minutes, bike or rower preferred)
- 2-3x LISS weekly (30-45 minutes, incline walk preferred)
- Never do HIIT before leg day
- Minimum one full rest day
Example Weekly Schedule
- Monday: Upper Body + 20 min HIIT
- Tuesday: Lower Body
- Wednesday: 45 min incline walk
- Thursday: Upper Body + 30 min LISS
- Friday: Lower Body
- Saturday: 20 min HIIT
- Sunday: Rest or easy walk
The Beginner's Progression
If you're just starting with cardio, don't dive headfirst into HIIT. Here's a smarter approach:
Weeks 1-4: Base-building
- 3-4x per week LISS
- 20-30 minutes
- Focus on consistency
- Build aerobic capacity
Weeks 5-8: Introduction to intervals
- Replace 1 LISS session with intervals
- Start with 1:3 work-to-rest ratio
- Example: 30 seconds hard, 90 seconds easy
- Focus on form and technique
Weeks 9+: Full integration
- 2x HIIT, 2-3x LISS per week
- Progress to 1:2 or 1:1 ratios
- Monitor recovery carefully
- Adjust based on performance
Common Mistakes I See
Mistake #1: Daily HIIT
Your body needs recovery time. Real HIIT is extremely stressful. If you can do it daily, you're not pushing hard enough for it to be actual HIIT.
Mistake #2: False Intensity
HIIT is HIGH intensity. If you can talk through your work periods, that's not HIIT — that's moderate-intensity intervals.
Mistake #3: Ignoring Heart Rate
Invest in a heart rate monitor. For HIIT, you need to hit 85-95% of max HR during work periods. For LISS, stay at 50-65%.
Max HR Formula: 220 - your age (approximate)
Mistake #4: Choosing Based on Fat Burn Myths
The "fat burning zone" is largely a myth for actual fat loss. Choose based on your schedule, preferences, and recovery capacity.
Special Considerations
If You're Over 40:
- Focus on LISS (3-4 times weekly)
- Limit HIIT to 1-2x per week
- Prioritize low-impact options
- Allow more recovery time
If You're Strength Training:
- Do cardio after weights or on alternate days
- Keep HIIT sessions short (15-20 min)
- Fuel adequately — don't do HIIT fasted if muscle preservation is important
- Monitor performance metrics
If You Have Joint Issues:
- Bike and rowing > running
- Swimming is excellent for LISS
- Incline walking works great
- Avoid high-impact HIIT
The Interference Effect Deep Dive
This deserves its own section because it's critical for lifters. Concurrent training (cardio + weights) can interfere with strength and muscle gains through several mechanisms:
- Molecular interference: HIIT activates AMPK, which can shut down mTOR (muscle growth pathway)
- Fatigue accumulation: Less energy available for lifting
- Recovery competition: Your body has limited recovery capacity
- Fiber type shifts: Too much cardio can promote slow-twitch fiber adaptation
Minimizing interference:
- Separate cardio and weights by 6+ hours if possible
- Do weights before cardio if in same session
- Limit high-intensity cardio volume
- Fuel properly
- Get adequate sleep
Practical Implementation Guide
HIIT Workout Examples
Bike Sprints (Beginner)
- 5 min warm-up
- 20 seconds all-out effort
- 100 seconds easy pace
- Repeat 8 times
- 5 min cool-down
Treadmill Intervals (Intermediate)
- 5 min warm-up
- 45 seconds at 90% effort
- 75 seconds walk
- Repeat 10 times
- 5 min cool-down
Rowing Intervals (Advanced)
- 5 min warm-up
- 30 seconds all-out effort
- 30 seconds rest
- Repeat 12-15 times
- 5 min cool-down
LISS Options Ranked by Effectiveness
- Incline Walking (3-5% grade, 3-4 mph)
- Easy on joints
- Can watch shows/read
- Burns surprising calories
- Cycling (comfortable pace)
- Low impact
- Can be done outdoors
- Great for recovery
- Swimming (continuous laps)
- Full body workout
- Zero impact
- Higher calorie burn
- Rowing (steady state)
- Full body engagement
- Low impact
- Builds back strength
The Bottom Line
After all the research and experimentation, here's my honest take:
For pure fat loss: Total calorie deficit matters more than cardio type. Choose what you'll actually do consistently.
For busy people: 2-3 HIIT sessions per week, but don't neglect some easy cardio for general health.
For strength athletes: Keep LISS as your primary cardio to minimize interference. Use HIIT sparingly (1-2x per week max).
For beginners: Start with LISS, build a base, then gradually add intervals.
For longevity: A mix of both. 2-3 LISS sessions for heart health and recovery, 1-2 HIIT sessions for metabolic and performance benefits.
Final Key Takeaway
Remember: The best cardio is the one you'll actually do. I've seen people get shredded doing only walking, and others using only HIIT. Consistency beats optimization every time. The person who walks 30 minutes 3x per week for a year will beat the person who does HIIT every day for 2 weeks then burns out. Play the long game.