Okay, it’s true that exercising first thing in the morning after an overnight fast burns more fat during the exercise session. But, there’s more to it.
Fat is utilized at all times as is protein and carbohydrate. The percentages of each that are used shift depending on our level of fitness, intensity level and diet (including time from the last meal).
We burn a greater percentage of calories from fat at low intensities. (For example, when we are sleeping.) As our intensity of activity increases, we begin to burn a lower percentage of calories from fat. But, we are burning more total fat calories, because we need more fuel to exercise than we do to sleep.
At the end of the day, it comes down to the balance of fat and energy. If, after 24 hours, you have used all of the fat you have consumed, it will not be stored and you will maintain your weight.
Exercise is an important aid in creating caloric balance. The focus should not necessarily be on the fat you burn during your exercise session, but the amount burned throughout the day (along with the fat consumed).
Of the three factors (fitness level, intensity and diet) that affect the three choices of fuel (carbs, protein or fat), intensity level makes the most impact. At lower levels of intensity, fat is predominant. Many of our subscribers tell me that they barely feel that they are working when they choose the "fat burner" program on the Stairmaster or bike. The reason is that the lowest exercise intensities burn the most fat. But, that may not be the best use of your time if your goal is fat loss. As exercise becomes more strenuous, carbohydrates become the primary source of fuel. However, fat is still used. The rate of fat used is higher during strenuous exercise, because the metabolic rate increases faster than the percentage of fat used decreases.
If you exercise moderately first thing in the morning on an empty stomach, more fat is utilized than later in the day when meals are consumed. An overnight fast leaves you in a state of higher levels of free fatty acids and lower insulin levels.
The more fat in your diet, the more you will be able to use it as energy during moderate exercise. Keep in mind that the trade off is that a high fat diet will not improve your performance. The more fat you eat, the less carbs you will be able to store for energy (and then performance suffers.
The more fit you become, the better you will be able to utilize fat. So, if you and a buddy are both on the treadmill running at the same rate and weigh the same, but you had been regularly running for a year and your buddy just started, you would burn more fat due to a faster metabolic rate and use a higher percentage of calories from fat.
There are several reasons to exercise in the morning on an empty stomach, but the bottom line is to exercise when it feels best for your body and when it best fits your schedule. Just be consistent. Keep in mind the fat you are consuming should be balanced with the fat and calories you are expending.
As a rule of thumb, never add fat to your diet. There’s plenty of naturally-occurring fat in foods. Attention should be focused on getting in regular workouts to experience the wide range of benefits available from exercising, including burning fat.
I hope you were able to follow along with this often misunderstood concept of fat burning zones and timing of meals. If you have any inquiries, please post on my board Ask The Expert.
Thanks to tescodiets.com who have provided this article.