Eating for fat loss

Last week at Uni I performed a sub max steady state exercise test on a ergo bike (a technical stationary bike).

The test was 6 x 5min stages at increasing intensity. Each stage I breathed into a Douglas bag which was then analyzed. This told us whether I was using more fat or carbohydrate as fuel during each stage of intensity. Pretty cool!!

Week 1 was under normal dietary conditions and week 2 was after a 4 day carbohydrate depletion.

During this depletion my carbohydrate intake would have been around 50g per day.

The idea of the test was to compare the two and see wither there was a change in the way fat and carbohydrate was used during the test. As you can imagine I used fat as a fuel source for much longer during the second test because there was a reduced pool of carbohydrates for the body to use.

This meant I had used more fat during the second week!!!

Fat is used as a fuel source at low to moderate intensity due to the large cost of oxygen to metabolize it. Basically it’s a long process for the body to complete and requires plenty of oxygen to do so.

Carbohydrates however cost the body less oxygen to metabolize and this is why it is the preferred fuel.

So as intensity increases fat utilization lowers and carbohydrates dominate.

So what real world applications can we make from this?

For fat loss

• Once glucose (carbohydrates) hits the blood, the body suppresses fat breakdown and switches to using the glucose.
• To increase fat loss we can lower our total daily carbohydrate intake so we can empty our stores of carbohydrates more easily during exercise and tap into fat.
• Eat plenty of good fats, protein and some good complex carbohydrates in the form of whole foods.
• For weight loss, at night time limit your carbohydrates and then again in the morning or skip breakfast. Then get to the gym and train in a fasted state. You have fasted from dinner to after your workout, so you’ll be training with less carbs in the tank!

Improve performance during endurance events

• If your a runner (or other endurance event) and would like more energy during your run then you can train your fat oxidization pathways as this is highly trainable.
• Train in a carbohydrate depleted state to improve your fat oxidative pathways. This is highly trainable.
• Use a high fat, high protein race diet. (I race on mostly fats and proteins with some carbohydrates and feel fine)
• The GI track can only absorb about 60g of glucose per 60mins.

This is an oversimplification and there is a lot more to it then I’ve simply stated above. I’ll be writing another blog on metabolism which will explain it in more detail.

What type of training for fat loss?

Based on the information above you may be thinking “great, i can do low to moderate exercise such as walking to lose fat”. Well yes and no. It depends on a few factors.

If you have not been training lately then yes it may work. The simple change of increasing your daily activity may start the fat burning process. There are also other things to take into account that go with your newfound exercise regime. When you decide to start exercising more, you most likely eat better afterwards too which will aid in fat loss.

High Intensity Interval training (HIIT) has been shown to be the greatest tool when your goal is to burn fat.

Why? Is this not high intensity burning carbohydrates?

Yes, you will burn carbohydrates at the time BUT it’s what happens when you stop that counts.

EPOC- Excessive Post-exercise Oxygen Consumption.

After that gut wrenching, brutal, make you feel sick HIIT session, your body needs to return to its base line or normal state.  Hormones need to come down to base line, muscles must cool, the heart needs to slow down, while you scrap yourself off the floor.

All of this costs the body energy, and to produce that energy you need oxygen and fat! You have stopped exercising and now the body can burn fat as you breath in the required oxygen to do so.

Besides EPOC there are also physiological adaptations that cause you to become more efficient. Put simply, a trained person can burn fat longer than an untrained person due to more efficient muscles.

So what to eat.

Following is a sample of what I ate during the 4 day carbohydrate depletion

Breakfast

Eggs, bacon, salad….

Or protein shake and handful of almonds

Lunch

Lunch box full of salad and meat. Kale, tomato, avocado, almonds, mushroom, cottage cheese or ricotta, capsicum….

and Protein shake

Dinner

Steamed veggies and chicken or beef. Or try a Taco salad

Snacks