I’d like to pose two questions:

1/ Do low-carb diets work?

2/ Does eating carbohydrate make you fat.

According to many diet books and internet forums, carbohydrate is single-handedly responsible for the obesity epidemic sweeping through the western world.  The thinking behind this assumption is  that when you eat a meal containing carbohydrate it causes an insulin response that leads to fat-storage.  It is claimed that eating a diet predominately comprising of protein and fat offers a “metabolic advantage” that puts you in “fat burning mode”.  It is also claimed that two diets containing the same amount of calories—or isocaloric diets—will have different outcomes when it comes to achieving fat gain or fat loss.

This, of course is just wishful thinking.  There is no evidence that the metabolic advantage theory is true.  It would be easy for its advocates to prove it held water, but they can’t and the evidence points at the hard truth: that a calorie deficit is needed to lose fat—always.  The diets that advocate low-carb lifestyles only work because they are low calorie, not because they are low carb.  One of the most successful diets—The Zone—is a low calorie, adequate protein diet.  The Atkins diet—an almost zero carb diet—would never have worked if the calories weren’t lowered, and how were they lowered—by removing carbohydrate from the diet.  It’s hardly magic.

Does this mean that low-carb diets are a bad idea?

No, they are a good idea for a lot of people.  They do work, but not for the reasons the low-carb dogmatists would have you think.

The first prerequisite of a healthy fat-loss diet is that it’s hypocalorific—that is you it contains fewer calories than get used in any given period of time.  So, let’s say you notice that if you eat 2000 calories a day, your weight neither goes up nor down.  In this case, to lose fat you’d need to eat fewer than 2000 calories each day.  Most people can get an idea of what this figure is for them by multiplying their bodyweight in pounds by 11.

Bear in mind that a pound of fat contains about 3500 calories, so if you wanted to lose one pound of fat per week, you’d need to create a deficit of 3500 each week, or 500 calories per day.  Remember in the hypothetical example above, you have worked out that 2000 calories a day is your maintenance calorie intake, or the amount of calories you need to eat to stay the same weight.  That means that you will need to eat 1500 per day to lose one pound of fat in one week.

The second prerequisite of a successful fat-loss diet is that you eat adequate protein.  This is to ensure that the weight you lose is fat and not healthy bodyweight such as muscle, connective tissue or bone.  A good minimum amount of protein to eat is 0.8g per pound of bodyweight.  So if you are 180Ibs, you will need to eat 144g of protein everyday.  This is more protein than most people eat.  Protein contains 4 calories per gram so in this example your protein intake will have cost you 576 calories.

The third prerequisite of a healthy fat-loss diet is that you consume adequate vitamins, minerals, fibre and anti-oxidants.  Guess what?  You can cover this the whole of this third prerequisite by eating plenty of different vegetables and some fruit everyday.  Bear in mind that an apple contains about 100 calories and banana contains about 120 calories. Starchy vegetables contain roughly the same as a banana and leafy vegetables are low calorie.  If you’re eating 3 meals a day and having a piece of fruit with each meal and plenty of leafy vegetables at each sitting—30 to 40g of carbohydrate per meal or 100g per day sounds reasonable—adding another 400 calories to your daily total.

The fourth prerequisite of a healthy fat-loss diet is that you eat adequate fat—especially EFA’s—that’s Essential Fatty Acids.  EFA’s, particularly Omega 3, are found in oily fish, flax and walnuts.  Aim for about 2.5 to 3g of omega 3 fat each day.  Monounsaturated fat should make up the bulk of the remainder of your fat consumption, keeping saturated fat intake to a minimum.  There are certain vitamins that need fat to be absorbed by the body so a small amount of healthy fat is essential.  Remember you’ve worked out already that you daily calorie intake should be 1500 to lose fat, 576 of which has already been spent on protein and another 400 calories has been spent on carbs—that leaves 524 calories to spend on fat.  Fat contains 9 calories per gram, so 524 calories of fat equates to 58 grams of fat per day.  This is not much fat and should be considered a minimum.

So looking at the numbers above, you can see that once you establish the caloric deficit, consumed the must-haves—such as adequate protein, essential fatty acids, some fruit, and plenty of vegetables, there’s very little room for anything else, let alone a plate of pasta (which contains about 70g of carbs or 280 calories, very little fibre, negligible amounts of vitamins, minerals, antioxidants and no essential fatty acids whatsoever).

Additionally, eating protein—or meat, fish and eggs—will also keep you feeling fuller for longer whereas eating a higher carbohydrate diet—especially simple carbs—will cause ups and downs in blood sugar which in turn causes hunger.

So, do low-carb diets work?

Yes, because any successful, healthy fat-loss diet will need to be low-carb to achieve its goals.  That’s why low-carb diets work, not because they are magic but because the only realistic way to eat everything you need each day and still remain with the calorie budget is to remove some carbohydrate.

And the second question—do carbohydrates make you fat?

No they don’t literally make you fat, eating too many calories make you fat, but the easiest way to eat too many calories is to eat a high carbohydrate diet.