If you have ever heard someone saying fat loss or fat gain is ‘simple thermodynamics – calories in, calories out’, or if you have ever heard or read the only way to lose fat is to enter a diet that has a calorie deficit (less calories in than going ‘out’) then this is critical information you cannot afford to miss.

Everyone should be taught this information in school. This couldn’t have come soon enough. It’s the missing piece that I had always been looking for, but never found easily. Completing a recent cross-country drive gave me a chance to listen, uninterrupted, to an excellent audio book on the topic, and I have found it revolutionary.

Its easy to be overwhelmed and confused with all the stories in the media about weight management, obesity, fat loss, people gaining weight, etc. I have read, for years now, so many articles that all hinted at something being a greater cause than all the little minor details that would be written about, and yet no one actually just put the finger on why exactly it was that I or you might have some excess fat on us, while other people don’t.

It wasn’t until this book that I finally ‘got’ it. The sense of relief was immense, and beyond that, the absolute need to tell as many people as I could about it.

So, I will try to keep this as straightforward as possible, because this is important.

At it’s most basic, we gain fat due to carbohydrates opening the pathway to food energy being stored in fat cells.

To go into any more detail would be to add extra information, rather than summarize, however, so the above statement is the basic formula of how the human body gains fat.

Of course, I expect you would like more detail, and I am only too happy to share it with you.

Effectively, carbohydrates in food are digested and become glucose (sugar) in the bloodstream. How quickly they are digested, and how much there is of them is what affects how much glucose there is in the bloodstream after eating. This is where the concept of Glycemic Index, and Glycemic Load come from.

The more carbohydrates, the higher the blood glucose. The faster they are digested, the faster blood glucose rises.

So this is where insulin comes in. One of insulin’s primary roles in the body is to act as the ‘hall monitor’ in the bloodstream, to ensure that glucose concentrations aren’t getting too high as this can be dangerous.

You may have heard of the term ‘insulin spike’ or ‘insulin response’ when people are talking about food – in particular carbohydrates. This is because neither protein nor fat evoke a response from insulin. The importance of that will become obvious soon.

Insulin is what tells cells in the liver, muscles and fat to take in glucose from the blood, and store it.

This is important because once the muscles and liver have as much as they can take, if there’s more ‘excess’ glucose in the bloodstream, it all needs to be stored in fat. This is after some is taken in by the fat while the muscles and liver and taking some in – and this depends on a lot of factors, including genetics.

So, when you or I eat a meal with carbohydrates, our insulin comes to our aide and makes sure our blood sugar level doesn’t deviate too far off course. It does this by sending glucose to fat cells, muscle cells and the liver. After some time, blood glucose lowers, and fat cells (and potentially muscle cells) are accessed for their reserves of energy, until eating happens again and the cycle restarts from the beginning.

If we eat many meals with lots of carbohydrates, then our insulin doesn’t get a rest, and we eventually become pre-diabetic, as the cells in the muscles, fat and liver become ‘deaf’ to the insulin, and the body produces more and more to get the same effect.

If we eat a meal with protein and fat, insulin remains almost completely dormant. It doesn’t need to control blood sugar, because the protein and fat don’t have the same effect on glucose levels in the blood.

And this is the really important part: Meals with fibre are digested slower, meaning blood sugar doesn’t spike and then crash down, but it steadily remains around where it should be. This means insulin’s job is much easier, and less needs to be produced. This is why slow carb works for so many people. And also why low carb diets are also so successful.

Now that we understand insulin’s job, we need to look at energy in the body.

If you eat enough, then you body is supplied with all the energy it needs. If you eat too little, it needs to take energy from fat stores. This is why so many diets work, right?

Well, almost.

If you eat less than your requirement, then the body does need to find the energy. However, it can look to the muscles for glucose, and to the liver too, before it goes to the fat. And if you eat another carbohydrate-heavy meal a few hours later, the body is yet again working to control blood glucose levels, though the effect is less if you have eaten less than you might otherwise have.

But there’s still an effect.

So here’s the most important part of this article, taken directly from Wikipedia:

Insulin stops the use of fat as an energy source.

Let’s consider that again.

Insulin stops the use of fat as an energy source.

Said differently, in another part of the Wikipedia entry:

Decreased lipolysis – forces reduction in conversion of fat cell lipid stores into blood fatty acids.

Therefore, whenever insulin is present, fat cannot be used as energy. Glucose must be used.

Why is this the case?

If we take a look at the earlier example of there being excess glucose in the blood, insulin needs to ensure that it is used by the muscles, and liver, as much as possible, as well as by the fat cells, to adjust the level of blood glucose. Of course it will inhibit any other energy source, when there’s already more than enough glucose to go around, and it might need to store a good portion of it in the fat cells.

So insulin blocks fat entering the bloodstream from the fat cells, because it would put us in danger of having a blood sugar level higher than the safe range.

If you think about this then, reducing portions of commonly-eaten foods, like breads, pastas, cereals and potatoes only reduces the number of carbohydrates, but doesn’t mean insulin will not be alerted to the presence of glucose in the blood. Therefore, it is after digestion, and after the glucose has been used in muscles, the liver and fat, that fat is an acceptable energy source. If the next meal comes in soon after, any fat-burning time is kept to a minimum. Overnight, fat becomes the primary fuel source, as food energy is used up in the body. It’s convenient that way. But in the morning, glucose becomes the primary source, if cereal and milk is eaten, or if toast and jelly, or honey is eaten. Effectively, insulin is woken up, and begins its job for the day.

Controlling how insulin is working is less or more important, depending on if you’re the type of person who stores fat easily, or burns it in your muscles. This choice the body makes about where to direct energy is complex, and is affected by many, many different factors. To suggest that all people process their food the same way is silly, but to suggest that every body stores or burns energy from the bloodstream in the same way is crazy. Everyone is different.

Therefore, everyone has a unique circumstance, in which fat loss, weight maintenance or fat gain can be ‘tuned’ according to carbohydrate intake (grams/day).

So, all those calorie controlled diets out there miss an important fact – its the fact that they (accidentally) control carbohydrates that they have such success. Most people who eat 60% carbohydrates will cut out a certain amount of carbohydrates when they control their calorie intake – it just makes sense. 60% of 1500 calories is much less than 60% of 2200 calories. In fact, this example shows that on the calorie controlled 1500 calorie diet, the dieter would be consuming 225 grams of carbohydrates per day, compared with the unrestricted eating which yields 330 grams of carbohydrates per day. That’s a substantial 105 grams per day difference, even if the dieter was unaware of their carbohydrate, protein and fat intake, and was focused only on calories.

That means the body has a much better chance of having times throughout the day to burn fat for energy.

But ultimately, as I’ve learned, its not about calorie control, but carb control and timing. Carbohydrates before activity will be more likely to feed into the muscles, however carbohydrates before sitting watching tv will be more likely to feed into the fat cells, as the muscles will have a full store of glucose (as glycogen) already, and the excess glucose from the bloodstream needs a place to go. With insulin active to keep glucose levels controlled, any fat burning is blocked.

Slow carb offers a simple approach, but incorporating carbohydrate sources that have a lot of fibre, and including protein and vegetables with those carbohydrates, making for a very slow digestion, and a slow entry into the blood. This means many people might be burning fat for energy in between meals, some people only overnight. Importantly, however, it’s much less likely that any excess will need to be stored – because slow carb is about eating enough to feel satisfied. The body is smart, when given the chance, and knows how much it needs. Many people find they eat less than they expect – this is because the body can count fat stores as another ‘food source’, and might pull in 100-300 calories of fat per day, resulting in less appetite.

So now you know.

This isn’t some fad diet advice – this is biochemistry, and this is body-science. Just about every diet system or weight loss pill out there is based on the idea of getting your body to burn more energy in muscles, and store less in fat cells, or for you to burn more energy in your muscles, and therefore direct more energy that way. Many supplements work by mobilizing fatty acids in the fat cells, or inhibiting the fat cells’ ability to store more fatty acids, whilst others work to try to divert more energy to the muscle cells. Some talk about metabolism – many of these increase your burning of energy by raising your temperature and/or heart rate.

Slow carb gives you a chance to give your insulin and blood sugar levels a rest. It also does so in a way that doesn’t leave you starving and dreaming about food all day long, like calorie controlled diets do.

If you’d like to read more about why we get fat – and what to do about it, please click here for Gary Taubes’ book on Amazon.

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