Fat Loss: Cardio Timing!

Jeff Behar answers a reader's question about the best times to do cardio and how much should be done. Learn from the best!

From: Pauli Blamont
To: Jeff Behar
Subject: Pauli Blamont on losing weight!

Hi I have a quick question.

I am 6'5" and 315 pounds! I run about 4 hours total a week. Which is better. To run 2 hours Sunday and two hours Monday, or should I spread my sessions out more? Like for example 1 hour Sunday, 1 hour Monday, 1hr Tuesday, and 1hour Wednesday!

Does it matter?

Jeff's Response


Your question is a good one.

Running is an excellent way to lose weight, however at 315 pounds I am concerned that the road work can take its toll on your body. Running outside can cause injuries due to the high impact. Many runners experience several injuries to their joints as a result, that often will sideline them therefore preventing you from reaping the benefits that you are trying to seek.

If you are like most "weekend runners" you run locally where there are vehicles. Running in such areas can be very hazardous to your health. The most obvious hazard is the oncoming traffic (so wear high visability/high reflective clothing). A second hazard often overlooked is the actual air you will breathe. Ambient (outside air) in all major cities contains varying amounts of toxins.

Our bodies are pretty resilient to a number of these gases for several reasons. However, running presents an additional problem because you are now breathing more of this air, and you are winded, so you are breathing it deeper into the smallest regions of the lungs. Running alongside vehicles exposes you to elevated levels of dangerous car emissions such of NOX and SOX (including hundreds of other by products of incomplete combustion).

These potential hazards, in my opinion, far outweigh the benefits of road work. Additionally, today, there are so many additional alternatives that can actually give you a better (and safer) more effective workout. My preference would be for you to do some sort of lower impact cardio where you would reap the benefits without potentially injuring yourself.

You can do this through cardio classes (boxing, aerobics, spinning, etc.), swimming or using any one of a number of cardio machines. Most gyms today offer a variety of cardio equipment such as Stair Steppers, Rowing Machines, seated and regular stationary bikes, Nordic challenge machines, just to name a few.

Today's machines can measure heart rates, track calories, alter your elevations, intensity, speed, and even make you a protein shake (just kidding). My favorite machine is the elliptical machine because the motion seems to be the most natural for me and causes the least discomfort to my joints and lower back.

Some machines feel unnatural for different people, so get on different makes and models and choose a machine that provides the most natural feel without causing pain. My additional suggestion is to alter the equipment you use to keep your body challenged.

If you still prefer the old fashioned way and prefer to do road work, make sure you have very good sneakers and be cognizant of the potential damage that such road work can do. Also try to jog at hours of the day when the heat and pollution levels are more favorable to your health.

Now getting back to your question as far as which approach is the most optimal:

  • To run 2 hours Sunday and two hours Monday, or
  • Spread my sessions out more. (e.g, 1 hour daily)

The most important thing you already have: the desire to get in shape and I applaud you for that. However, since you asked the question, I will share with you my personal experience which has been that by spreading out the sessions will prove more beneficial (as long as you reach your target heart rate). Why is this my preference?

Because it is not the calories you burn during the run that are the most important, it is the calories you burn for the next several hours because you raised your Basal Metabolic Rate (BMR). The calories that you will burn literally while doing nothing, will exceed the calories initially burned. This is why I favor 30-40 minute sessions over split routines (am and pm) if you want to optimize fat burning.

Morning Cardio

I do advocate doing cardio first thing in the morning before eating any carbohydrate meal. If you run or do cardio after training (like I do) I would advocate eating your protein, Branch Chain Amino Acids (BCAAs) and other supplements (including CLA) before doing the cardio, and it will actually further supercharge fat loss while preventing muscle catabolism (wasting).

I do recognize that there is no conclusive evidence that morning cardio is the best method, however there's quite a bit of scientific literature supporting that doing cardio prior to ingesting carbs will burn more stored body fat (because glycogen is not burned).

There are others that will argue with me here because they believe in the energy balance hypothesis, which states; the time of day you burn calories or eat calories doesn't matter, as long as you burn more calories than you consume in each 24 hour period.

Those that subscribe to this theory also believe that if you eat your meal before the cardio you will burn glucose during exercise, but then will burn the same amount of fat as the other method, just later in the day. I disagree with this simplistic approach because it assumes that all calories are not created equal. We all know that all calories are not created equal.

Certain quality foods burn quicker (which is why there is such a thing as the glycemic index), and why there are so many different diets out there. In fact, if we were just counting total calories believing that all calories are indeed the same, then why is there so much fuss over ratios of carbs, protein, and fat?

Also if calories are just calories and time did not matter then why is there plenty of support regarding eating smaller more frequent (5 or 6) meals a day than 3 square meals a day.

Forget what is "optimum" for a moment. I believe that the most important issue for someone to be successful at burning fat is that you are consistent. Consistent on your diet and in your training.

Consistent in subscribing to the principle that each workout you will challenge yourself a little more, since the body will be acclimated to the workout and will need more intensity to continue to make the gains you will come to expect and love). It is my experience that it is the lack of consistency is what derails many from their goals. So, getting the cardio done is the most important factor.

Favoring The Early Morning Approach

Here are the scientific reasons as to why I favor the morning approach.

Your body's glycogen levels will be lower in the morning (assuming you last ate at dinner time and have essentially fasted for 10-12 hour fast). Doing cardio without eating causes your body to mobilize more fat because of the unavailability of glycogen. Blood glucose levels are also lower after an overnight fast so you will burn more fat which will be used for energy.

After fasting your insulin levels are the lowest. When you consume a meal, especially one with carbohydrates your body releases insulin which interferes with the mobilization of body fat. Because there is less insulin present before eating after a 10-12 hour fast more body fat is burned when cardio is done in the morning.

Note: this is also why many "fat burning" or carbohydrate blocking products contain several ingredients which have shown to reduce or regulate blood insulin levels.

Eating immediately before cardio also inhibits fat burning because you will first have to burn off what you ate first before your body will burn stored body fat.

When you do cardio in the morning, your metabolism stays elevated for a period of time after the cardio workout is over. Understandably, this is also true if you do it in the evening however if you go to bed before the benefit is over you will not get the same result because scientific research supports that your metabolic rate drops off substantially as soon as you go to sleep.

Cardio in the morning will give you an energy boost throughout the rest of the day.

It can also regulate your appetite and assist you with controlling cravings and binging.

You get the workout done before something occurs during the day that prevents you from the workout (or before you are to tired from a tough day). How often has something just "come up" that has prevented you from getting to the gym later in the day? It is best to get the workout over as soon as you can to avoid this common pitfall.

Additional Things To Consider

If you lift before your cardio work than I would suggest ingesting some protein, some Medium Chain Triglyceride (MCT) Oil, and if you must, a small amount of carbs. Also remember to eat right throughout the day (do not starve yourself) so your metabolism stays high.

Taking thermogenic fat burners, adding MCT oils, and avoiding rapid rises in insulin levels will also help you reach your goals and look your best. Remember this important point (which most people ignore): Continue to train with heavy weights, even during a fat loss phase.

Using light weights will not keep muscle density on a calorie restricted diet. Additionally, lean muscle mass burns calories. This is why a bodybuilder can eat so many more calories than his/her less muscular counterpart.


I would change your current approach and spread out the cardio from 2 hours a few days a week to two 30 to 40 minute sessions 5 days a week, The morning and evening session will optimize fat burning because you will benefit from the elevated Basal Metabolic Rate (BMR) that the cardio causes. A single session would only cause the elevated BMR once a day.

The elevated BMR typically burns more calories than the workout itself. I am also suggesting that you do no more than 40 minutes of cardio on an empty stomach to spare muscle loss. Consuming a thermo drink, or coffee will not only provide a good pick me up but your body will run a bit hotter and you will burn a few more calories as a result.

Stay in touch and let me know how the advice works out for you.