Carbs and Fat: What Are They and Why Do We Care?

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The history of modern nutritionism has been a history of macronutrients at war: protein against carbs; carbs against proteins, and then fats; fats against carbs.
––Michael Pollan

Useful Links: Part 1 | Part 3

What Are Carbs?
 
No, the answer isn’t, “the enemy”. Carbohydrates are the main supply of readily available energy for our bodies. In particular, our brain can’t function without them. They come in two forms: sugary carbs and starchy carbs.

Sugary carbs are short chains of 1 to 10 sugar molecules, so they’re easy to break down, digest, and absorb into the bloodstream. This means they’re turned into energy right away, they cause a fast rise and fall in blood sugar level, and thus don’t keep us sated for long.
 
In their natural state, they’re found in fruit, vegetables, and milk; they’re also extracted from these products and artificially added to processed sugary foods such as desserts, smoothies, etc.
 
You don’t have to avoid these completely, but it’s recommended to privilege natural sources (fruit, vegetables, and dairy) and keep manufactured and processed sugary foods to a minimum.
 
Moreover, having sugary carbs in the same meal as starchy carbs, protein, and fat will slow down their rate of digestion and therefore help reduce the impact on blood sugar levels and keep you fuller for longer. For example, consuming a dessert as part of a meal may result in more satiety and a mitigated effect on blood sugar levels than the same dessert eaten alone three hours later.
 
Starchy carbs are much longer chains, made up of hundreds of sugar molecules, so they take longer to break down during digestion. For this reason, they cause a slower spike in blood sugar levels and provide more satiety. Examples of starchy carbs are potatoes, pasta, rice and other grains, and bread.
 
Wholemeal varieties – also known as “wholegrain” and “wholewheat” in the US – should be privileged as they contain more fibre. However, these days their white counterpart isn’t to be shunned at all costs, since white flour is often “enriched” (as you will see on the ingredients list) with micronutrients, such as vitamin B12, niacin, and iron. Nevertheless, the fibre content remains low, so try to combine white flour carbs with more fibre-dense ones.
 
Fibre is a particular type of starchy carbohydrate that comes in two varieties: water-soluble fibre (found in fruit, vegetables, oats, and some beans) and insoluble fibre (found in all plants, wheat, and rye). 25-30 gr of a combination of both per day are recommended to help with regularity, reduce overall cholesterol in the body, increase feelings of fullness, and slow down blood sugar levels alterations.
 
On the other hand, excessive intakes can cause constipation and prevent you from getting enough micronutrients, as fibre can absorb these from the food you’re digesting as it travels through your digestive tract. 
 
What Are Fats?
 
As above, not the enemy. In fact, they perform a variety of functions, which include keeping our bodies insulated and our skin hydrated, serving as a reserve energy source and as a major component in the structure of our cells, and transporting the fat-soluble vitamins A, D, E, and K through our body.
 
Like carbohydrates, natural fats are grouped in two categories: saturated and unsaturated fats.
 
Saturated fats are usually solid at room temperature and can be found in animal food like meat, whole milk, butter, and cheese, with some plant foods exceptions like coconut butter, and coconut and palm oil.
 
Unsaturated fats are liquid at room temperature. They can be monounsaturated (found in foods like peanut and olive oil, avocado, hazelnuts, and almonds) or polyunsaturated (found in fatty fish, seafood, polyunsaturated margarines, walnuts, Brazil nuts, seeds, and vegetable oils such as safflower, sunflower, corn, and soy oil).
 
There is a third variety of fats, called trans fats, which are artificially created from polyunsaturated fats. Trans fats are easy to use in the manufacture of fried foods, ready meals, and commercially baked goods. This is the only type of fat recommended to avoid altogether.
 
How Much Should We Eat?
 
Current UK guidelines advise that carbohydrates should make up 50-55% of your total calories, with sugars amounting to a maximum of 5%.
 
In order to support all the bodily functions requiring this nutrient, a minimum of 20% and no more than 30-35% of your calories should come from fat, with no more than 11% coming from saturated fat and 2% or less from trans fat.
 
It is also recommended to reduce fat and increase carbs, or vice versa, depending on personal preference, whilst ensuring a minimum 10% of your calories comes from protein. 
 
Lastly, saturated fat may not be the heart disease fostering monster that it’s been made out to be. In 2014, a meta-analysis of 72 studies on the correlation between heart disease and saturated fat could not prove that the latter is a direct cause of the former.
 
The Seven Countries study in 1958 promoted that idea. Its results, however, seem to have been cherry-picked to support the author’s original hypothesis, and they were then sensationalised by the media.
 
Although the jury is still out on the existence of a causative link between saturated fat and heart disease, the conclusion of the scientific community in 2017 was that replacing some saturated with unsaturated fat – particularly polyunsaturated varieties – may decrease the risk of heart disease. As a result, we shouldn’t eliminate saturated fat from our diet, but it would be smart to consume a higher proportion of unsaturated fat.
 
In Future Episodes:
 
Next week, Part 3 of the mini-series puts everything together, covering the concept of balanced meals and snacks. As a bonus, I will also include sample, simple meal ideas so you can get started on the right foot if you wish to improve your diet!
 
Your Turn:
 
What are your favourite sources of carbs and fat?