I'm not an expert in nutrition, but I want to understand more. I do like cooking but I've always missed the science behind it. I do exercise everyday (lifting weights and yoga mainly) and I also decided to become more aware of what I eat so I can plan what I'm going to eat a bit better based on my needs.

I'm currently reading through this book (Re-nourish from Rhiannon Lambert), which I think is simple and anyone can read it, and I think it's well written, it's not targeting body building at all it's just all about eating well.

The specific bit I want to understand at the moment is the difference between fats and carbs.

This is the definition I'm using for carbs (taken from the NHS website):

What are carbs? Carbohydrates are 1 of 3 macronutrients (nutrients that form a large part of our diet) found in food. The others are fat and protein.

Hardly any foods contain only 1 nutrient, and most are a combination of carbohydrates, fats and proteins in varying amounts.

There are 3 different types of carbohydrates found in food: sugar, starch and fibre.

Sugar: The type of sugars that most adults and children in the UK eat too much of are called free sugars.

These are sugars that are added to food or drinks, such as biscuits, chocolate, flavoured yoghurts, breakfast cereals and fizzy drinks.

The sugars in honey, syrups (such as maple, agave and golden syrup), nectars (such as blossom), and unsweetened fruit juices, vegetable juices and smoothies happen naturally, but these still count as free sugars.

Find out more about sugar

Starch: Starch is found in foods that come from plants. Starchy foods, such as bread, rice, potatoes and pasta, provide a slow and steady release of energy throughout the day.

Find out more about starchy foods

Fibre: Fibre is found in the cell walls of foods that come from plants. Good sources of fibre include fruit and vegetables, wholegrain bread, wholewheat pasta, and pulses (beans and lentils).

About the fat instead the NHS provides this description, doesn't seem to me they provide a definition, but they say why they're useful (such as absorbing vitamins for example).

Rhiannon Lambert in his book says:

Carbohydrates hold a special place in nutrition as they provide the largest single source of energy in the diet. Most carbs get brkoen down or transformed into glucose, which can be used as energy. Carbs can also be turned into fat (stored energy) for later use. Glucose is the essential fuel of our brains and the preferred energy source for our muscles during strenuous exercise. If you're naturally lean and physically active, a diet rich in carbohydrates is likely to enhance your performance and lifestyle.

This sentence here actually made me think.

1) Some people, like my self, don't eat before working out (for some reason I find more beneficial to exercise in the morning at empty stomach, just with water and later have breakfast). Would it be better instead to have breakfast? I guess the answer to this question might a potential yes but it should be conditioned to the glucose I would be taking by eating those carbs, therefore my question here is is there an actual "optimal quantity" of carbs to eat before working out?

2) Other question, since carbs become fat anyway, what's the point of eating fats (apart from the fact they make the food more tasty), is there a difference the I'm subtly missing? To fats come with other nutrients that carbs don't?

My apologies for my lack of terminology, as I said I'm still learning.

1 Answer 1


Carbohydrate intake will certainly affect your training, as compared with the fasting state. To provide a personal anecdote, if one of my athletes was struggling to perform during her morning session, it was invariably because she had not eaten, and she would simply be unable to complete the workout with the intensity that we were expecting. I would send her straight home.

This example, though, illustrates the importance of carbohydrate for performance—a correlation that is well researched and documented. If, however, you are not training for competition or peak performance, and if you feel comfortable, a meal before your bout of exercise may be unnecessary. And it may, in fact, be beneficial not to eat, since we metabolise more fat in the fasting state. Thus, it largely depends upon the reason for your exercise.

The quantity of carbohydrate you should eat, if you do, will depend on the requirements of your training. However, it is important that you give yourself enough time to metabolise the carbohydrate, so its sugar is held as muscle and liver glycogen and not blood sugars, since elevated sugars signal the release of insulin, which is deleterious to performance. The time needed will depend on the glycaemic index of the food consumed (type) and the total glycaemic load (quantity).

Although insulin controls the production or synthesis of fats in the body, we need essential fatty acids for health. (The term "essential" is used in a number of related contexts, referring to a nutrient that the body cannot synthesise, and which therefore needs to be consumed in our diets.)

A light to moderately light breakfast, taken one-and-a-half to two hours before training is ideal for most people, while a greater quantity or lesser time may lead to elevated blood sugar levels and stomach discomfort.

I hope that gives you a good start.

  • Can you give an example of "light to moderatly light" breakfast? Commented May 10, 2020 at 23:05
  • 1
    Naturally, this is relative to the individual, and to the type of food. However, I would normally think of a light breakfast as a couple of pieces of toast or one of the standard "servings" indicated on the commercial breakfast cereal boxes, with a piece of fruit. That is, "light" would normally refer to both the portion size (small) and the ease of digestion (starch). A moderately light meal might include one-and-a-half times that portion, and consist of a muesli of grains, nuts, seeds, and dried fruit, along with a piece of fresh fruit.
    – POD
    Commented May 10, 2020 at 23:37
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    Note that the fibre, fat, and protein in the muesli lowers the digestibility of the food, and hence the glycaemic index—but not the glycaemic load.
    – POD
    Commented May 10, 2020 at 23:40

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