Do Carbs Make You Fat? Thoughts On Exercise & Fat Loss

Thoughts On Exercise & Fat Loss

Something a little different today. What follows are my thoughts and the corresponding research on a handful of typical discussion points when it comes to exercise and fat loss.



Do Carbs Make You Fat?

To start let’s be clear that I don’t dispute that some people can and have lost weight following a low carb diet.

Granted it doesn’t work for everyone but for some the results are good.

However, one point that often comes up is how it’s carbohydrates that make you fat.

This is because carbs raise the hormone insulin which blocks the release of fat for energy and drives additional nutrient storage.(12)

Which is true, one of the functions of insulin is to promote the storage of nutrients and prevent the release of energy until levels have returned to normal.

Because of this function, there is a school of thought that advocates low carb diets. The reasoning being that it won’t keep your insulin levels elevated and therefore will be superior for fat loss.

Now whilst research does show that low carb diets can result in weight loss. (3456)

This is most likely because they cause you to eat fewer calories (78) — i.e. you’re in a calorie deficit — which is likely a result of an increased protein intake. (9)

Not because of its effect on insulin.

In my opinion, this point is summed up perfectly in the following quote from James Krieger at;

“One misconception regarding a high carbohydrate intake is that it will lead to chronically high insulin levels, meaning you will gain fat because lipogenesis will constantly exceed lipolysis (remember that fat gain can only occur if the rate of lipogenesis exceeds the rate of lipolysis). However, in healthy people, insulin only goes up in response to meals. This means that lipogenesis will only exceed lipolysis during the hours after a meal (known as the postprandial period). During times when you are fasting (such as extended times between meals, or when you are asleep), lipolysis will exceed lipogenesis (meaning you are burning fat). Over a 24-hour period, it will all balance out (assuming you are not consuming more calories than you are expending), meaning you do not gain weight.”

James also has a handy graphic to help illustrate this point:



So if carbs don’t make you fat, is it fair to make the assumption that it’s a calorie surplus that makes you fat?

I’d say so but read on to find out for sure.



Is The Ketogenic Diet Superior for Fat Loss?

The school of thought that carbs make you fat is often closely associated with the idea that a ketogenic diet (very low carb & high fat) is superior for fat loss.

However, there are again numerous research studies that disprove this.

In fact, in a study (10) conducted last year researchers compared weight loss between a high carbohydrate diet and Ketogenic diet.

The study presented its hypothesis as follows;

“isocaloric exchange of dietary carbohydrate for fat is predicted to result in increased EE [energy expenditure], increased fat oxidation, and loss of body fat. In contrast, a more conventional view that “a calorie is a calorie” predicts that isocaloric variations in dietary carbohydrate and fat will have no physiologically important effects on EE or body fat.”

What did they find?

There was no increase in body fat loss when using a ketogenic diet compared to a high carbohydrate diet and that although the ketogenic diet saw a rise in energy expenditure it was “near the limits of detection with the use of state-of-the-art technology” i.e. they could hardly tell it was there and as such it was insignificant. 

Ironically this study was conducted by the NuSI lab which was founded in part by Gary Taubes, one of the scientists that people who adhere to this school of thought often direct you to. Furthermore, this study completely debunked his theory that low carb, high-fat diets provide a weight loss advantage.

Other studies (111213) also support this finding, showing no difference in body fat loss when eating low carb (as little as 5% — 16% of daily intake).

The Bottom Line

Will some people do better going low carb? Sure.

Does this mean everyone should? No.

Is it more likely that body fat loss is a result of being in a calorie deficit? Yes.

Do you have to listen to me? That’s up to you.



Are Macronutrients Stored Preferentially?

If you’re in a calorie deficit you will lose weight regardless of macronutrient composition. (14

@@No macronutrient will make you fat or make you lose weight it’s overall calorie balance that dictates either weight gain or weight loss.@@

This is also what’s reflected in the research (15), which shows that both fat and carbohydrate overfeeding results in fat gain, just by different methods.

Carbohydrate overfeeding results in fat gain due to an increase in carbohydrate oxidation, decrease in fat oxidation and less stored energy being released. On the other hand, fat overfeeding results in fat being stored very easily due to the low rate of fat oxidation in response to overfeeding.

What about all those carbs that turn into fat?

Well, research shows the conversion of carbohydrate to fat (de novo lipogenesis) doesn’t significantly contribute to fat gain. (161718)

What does this mean?

Well researchers concluded that

“fat storage during overfeeding of isoenergetic amounts of diets rich in carbohydrate or in fat was not significantly different”

which means an excess of calories will result in fat storage regardless of their macronutrient composition.

Does this mean I am advocating a low-fat diet? NO. It means I’m advocating calorie control in the pursuit of changing body composition.

For a closer look at nutrient, storage check out Lyle McDonald’s superb article here.



What Constitutes ‘Low Fat’?

If we look at the general recommendations of a ketogenic or low carb diet we will find that carbs usually make up anywhere from 2–20% of daily intake.

In fact, it’s pretty clear what low carb is.

But again, what about fat?

Well, when you look at studies measuring the effects of a low-fat diet it usually makes up 13–25% of daily intake.

Which is at least 5% lower than my usual recommendation of 30% of daily intake from fat.

I say ‘usual’ because this number can and often is adjusted based on the preferences of an individual once they start eating this way.



Fat Loss Considerations for the Exercise Enthusiast

@@Do you just need to move more and eat less in the pursuits of body fat loss?@@


Well, actually. Sure, if you just want to drop some weight, give that a go. If you get yourself into a calorie deficit it’ll work.

In fact, you could lose weight without moving more at all if you wanted to.

However, for the average exercise enthusiast, training is an important consideration when it comes to changing one’s body through calorie and macronutrient manipulation.

@@What you need to do is optimise your movement and regulate your energy intake and output to achieve the results you want.@@

When considering fat loss, you should be asking:

  1. What training plan works best for me to reach my goals?
  2. What nutrition protocol works best for me to reach my goals?
  3. What combination of these 2 things will I be able to adhere to most consistently?

I personally recommend carbs in the diet when weight training to help fuel performance and aid in recovery. (19) In the same way, I advocate having enough fat in the diet to regulate hormones, allow the intake of vitamins and improve satiety. (20) Read more about both here.

@@I do not believe in excluding or severely restricting any macronutrient in the diet.@@

I also know I’m not alone in this opinion. Countless fitness professionals, athletes, bodybuilders, industry leaders and scientists agree. You just need to do a quick Google search to see that.



Exercise & Appetite: Can You Diet Successfully Over the Long-term?

Yes, you can.

It’s about managing intake.

It’s about thinking about what you put in your mouth.

It’s about not having the whole F-ing pizza and blaming your inability to out train your diet.

Yet somehow @@there is a collective warped attitude of “I should be able to eat whatever I want and still reach my goals”.@@

How can you seriously expect to do this if you’re unwilling to make any changes?

@@It’s like the whole dieting world is a group of spoilt kids who didn’t get what they wanted for their birthday.@@

Losing weight and in turn body fat to improve your health and aesthetics doesn’t have to be an all or nothing struggle.

@@Getting in shape is not all about having unlimited reserves of willpower and motivation, it’s about planning ahead, making smart decisions and becoming informed.@@

Another common fallacy is that;

“If you increase your exercise levels, your appetite increases.”

What actually happens is;

“If you increase your exercise levels, your energy expenditure increases meaning you can (if you want / need to) eat more before reaching a calorie surplus.”

Research supports this with one study (21) concluded the following:

“Exercise-induced weight loss is associated with physiological and biopsychological changes toward an increased drive to eat in the fasting state. However, this seems to be balanced by an improved satiety response to a meal and improved sensitivity of the appetite control system.”

Another study (22) summarised that;

“Many studies have demonstrated that acute bouts of moderately vigorous exercise transiently suppress appetite and this has been termed ‘exercise-induced anorexia’.”

Yet, another (23)said;

“Comparisons between sedentary and normally active individuals, or between enforced periods of rest or strenuous activity, generate little or no effect on levels of hunger or daily energy intake.”

Before going on to say;

“intake is not automatically driven up to compensate for energy expended. Reasons why physical activity often produces disappointing effects, rise from inappropriate food choices, a desire for self-reward after exercise and misjudgements about the relative rates at which energy can be expended (by exercise) or taken in (by eating).”

I think that last bit sums this up perfectly.



Exercise & Willpower

Someone once said to me…

“you can’t use “willpower” to overcome your urge to eat, any more than you can hold your breath while ignoring your body’s command to breathe. Sure, you can hold out for a little while, but your body always wins, whether it’s starved for oxygen or calories.”

Hm…sure you can, particularly if exercise doesn’t increase appetite as previously suggested.

No one is going to die because they did some exercise and ate in a moderate calorie deficit 300–500 kcals under their maintenance calories, nor is a little hunger going to cause someone to keel over and die.

Lack of oxygen on the other hand….well, I don’t need to tell you what that does.



Exercise & Weight Loss

Someone also once commented on some of my work saying…

“Exercise does not contribute to weight loss.”

My first response was…WHAT?!? Are you a real person, did you just say that?

Then I thought for a minute and said, “no no be fair”, because in a way they are right;

  1. You can lose weight without exercise…if you eat in a calorie deficit
  2. Exercise won’t contribute to weight loss…if you eat in a calorie surplus

But I shouldn’t have to tell you that it’s the combination of exercise and diet together that provide the best results for weight loss as opposed to either one on its own. (24Besides if we go back to diet for exercisers then calories and macronutrients in combination with diet directly influence body composition. (25)



Intentional Weight Loss & The Long-term

Someone once said this to me…

“There are no intentional weight loss diets that work long term. But you can prevent yourself from gaining weight by nurturing yourself with food, getting sufficient sleep, and finding joy in your life. Then, maybe, you will drop weight unintentionally, and find yourself in the lucky 5% group of people who successfully maintain weight loss. But no guarantees…no sugar coating here…. just the facts.”

My thoughts?

Couldn’t nurturing yourself with food be considered calculating your calorie and macronutrient intake for some people?

I’m pretty sure it could.

Does that mean me and the comment writer are in agreement that long-term weight change can occur through the manipulation of calories?

I’d like to think so…but I doubt it.

Thankfully, this is backed by research (2627) and this is a direct quote from one of the studies:

long-term weight loss maintenance is possible if individuals adhere to key health behaviours.”

Which makes sense. You’re not going to sustain weight loss if you go straight back into a calorie surplus.

Common sense here people.

As for rebounding, it does happen but it’s largely down to a variety of factors and does not happen to everyone.

Often, it’s due to a lack of knowledge about nutrition combined with unsustainable eating habits used in an effort to rapidly lose weight with no thought for the future.

Which brings us back here…

“Reasons why physical activity often produces disappointing effects, rise from inappropriate food choices, a desire for self-reward after exercise and misjudgments about the relative rates at which energy can be expended (by exercise) or taken in (by eating).”


Summing Up

At the end of the day, everyone has their own opinions on this topic and this post won’t please everyone, nor does it have to. If you like what I do and say, awesome. If you don’t, then that’s ok too, no hard feelings.

@@Ultimately you should choose to adhere to whatever training programme and nutrition protocol that works best for you…whatever that may be (provided it’s not damaging to your health).@@

Thanks for reading and good luck on your fitness journey.