Low Fat vs Low Carb Diets for Fat Loss

How do we burn fat?

If you want to understand how to lose fat, you must first understand how your body burns fat. So let's get scientific for a minute.

One of the main functions of body fat, or adipose tissue, is to store energy in the form of triglycerides. A triglyceride is a molecule made up of three fatty acids joined to a molecule of glycerol.

Triglycerides, or fats, are a really great way of storing energy because they can store much more than other macronutrients. For example, one gram of triglycerides stores nine calories whereas one gram of protein or carbohydrates stores about four calories, meaning they’re less energy efficient.

That said, our body does store some carbohydrates in the form of glycogen in our muscles and liver, and uses it to maintain our blood glucose levels when we haven’t eaten or when we’re performing high intensity exercise.

When we’ve not eaten in a while, blood glucose levels are normal, and we’re not exercising intensely, our body gets energy from our body fat. An enzyme called hormone-sensitive lipase breaks down triglycerides into glycerol and fatty acids. These fatty acids then get exported out of the fat cells and are transported in the blood by a protein transporter called albumin. These free fatty acids travel around the body to provide fuel for our cells. Simple. So, if we burn more fat from our fat cells than we eat, over time we will lose body weight.

But that’s just fat. When we eat a balanced meal with a mixture of protein, carbs and fats, something entirely different happens. The protein and carbs are absorbed directly into your blood stream from the gut in the form of amino acids and sugars. The increase of blood sugar and amino acids causes the body to produce insulin to bring blood sugar levels back down to normal.

Insulin brings your blood sugar down by inhibiting hormone-sensitive lipase. In other words, we don’t can’t break down any more fat. This means your body must instead burn carbohydrates or amino acids for energy.

Insulin also increases storage of glucose and free fatty acids to help remove them from your blood. Glucose is stored as glycogen, but if your glycogen stores are full, then glucose can be converted to fat in the liver and stored as body fat.

So, obviously from this explanation, the key takeaways would suggest that if you eat carbs, you’ll raise your insulin and start storing fat. And yes, this is basically what we’ve said, but it’s way too simple of a way to think about things and ignores a vital point: energy balance.

Energy balance

No matter whether you eat carbs or fat, your body still needs the same amount of energy to function. And if you’re not eating enough food to meet those energy needs, you’ll be in a negative energy balance and lose body fat. On the other hand, if you consume more energy from food than you need, you’ll be in a positive energy balance. The extra energy will be stored as fat, which over time will lead to weight gain.