Now that the most complicated and potentially confusing part is behind us and we know our heart rate values relative to VT, LT, and RER, we can actually start programming for fat loss.

The overall concept and plan of attack here is pretty simple. We want to spend 1-2 hours each week doing cardio with ~80% of our time burning fat at or just above our VT (within 5-10 bpm of your target HR is fine) and the remaining ~20% at or above our LT focused on pure high intensity interval training (HIIT) and/or lactate threshold training (LTT). This split allows us to maximize our rate of fat oxidation and increase our aerobic capacity thanks to quite a few pretty cool physiological adaptations – we’re essentially training our bodies to more clearly recognize which exercise conditions should burn fat for fuel versus those that should rely on carbohydrates.

Aerobic conditioning directly targets fat loss through low intensity steady state (LISS) cardio, leading to better general oxidation efficiency during non cardio based activities. Regularly engaging in cardiovascular exercise also causes the type 1 fibers in our muscles to become better at oxidizing fats by stimulating protein synthesis and increasing their mitochondrial density. With greater mitochondria content in our muscles to metabolize fat, we also get to benefit from elevated post-exercise oxygen consumption (EPOC) – burning fat at rest after a workout.

Because we know that fat utilization decreases as exercise intensity increases, working as close to our VT (RER of 0.85) as possible during longer aerobic sessions is key. The heart rate range at VT gives us a great point of compromise between max calorie burn per minute and fat utilization percentage. This intensity level is also easy enough to be repeated multiple times throughout the week with a decreased risk of CNS fatigue accumulation if sessions are capped at 20-30 minutes (not including resistance work) and limited to 4-5 days a week. Do your best to stick to these upper limits to avoid unnecessary strength and hypertrophy losses.

Running and walking are fantastic aerobic exercises and highly recommended. Many of us spend so much time indoors with work that getting outside is a great change of pace. Along with the potentially therapeutic scenery, propelling yourself forward with a natural movement pattern is preferred over the use of a stationary machine due to the additional physical requirements of the exercise. When we walk/run outside, our bodies must continuously propel themselves forward (greater energy demand than on a treadmill) and use core musculature to remain upright (better posture and balance). There are no rails to lean on or belts to keep you moving as you walk through your neighborhood listening to an audiobook or podcast, you do the work. If you have the ability to get outside, please do it. With that said, using a treadmill is totally fine – the aerobic exercise you choose should be one that you enjoy and are able to repeat consistently. Stick to your target heart rate and do what’s best for you.