1 CALORIE RESTRICTION
Not all calories are created equal
There are, of course, diets that simply restrict calories. This includes portion control – basically eating a little less of everything – which is very effective,
but difficult to stick to. The issue is we
have our recipes that we use, and it is
difficult to reduce it by 20 per cent, say. Like if the original recipe called for one
or two eggs, how do you reduce that by
20 per cent? So that means you have to
serve yourself less, but that would leave
20 per cent of the unfinished meal in
the pot, tempting you all night! That is why the use of meal-replacement
shakes are popular. You simply make up an 800-calorie shake, and consume that. These shakes are nutritionally
complete, and effective in the short
term. It is, however, very difficult for most people to stick to these shakes for
any length of time, if only because of
the monotony. So I think these shakes
are useful to lose the weight initially, but alternative methods would be
required to keep the weight off.
Another popular approach is group support, including programmes such as
Slimming World and Weight Watchers. While each has their own unique
selling point, they all harness the fact
that you are more likely to do
something if you are doing it with somebody else. It is important to remember that because public ‘weighins’ are typically part of such programmes, they are going to be ill-suited to those who hate such events.
Then there are the intermittent fasting and time-restricted eating (TRE) approaches. The most common variation of intermittent fasting is the
5:2 diet, where one eats normally for five days, and then restricts calorie intake to 500-600 calories, for two days.
TRE limits the amount of time in the day that one consumes food, typically to a six- to eight-hour window. Both
undoubtedly create a calorie deficit for
many people.
The question is, aside from the reduction in calories, are there any
additional metabolic benefits? The
underlying concept is that during the fasting phase you allow your body to use up the carbohydrates from your muscles and liver, stored in the form of glycogen, so you begin to burn fat
instead. While there is some evidence
of effectiveness of both diets in mice, the latest human studies do not see any
significant advantage over and above
the reduction in calories, for either intermittent fasting or TRE.
How about calorie counting, because
aren’t all calories equal? Well, all
calories are equal once they are in us, as little poofs of energy. However, remember that we eat food and not
calories, and some food takes more
energy for our bodies to extract the calories from. This is why the source of
the calories, whether from a steak, a carrot or a doughnut, makes an enormous difference. While calories are a useful reflection of portion size, they are not a marker of the nutritional
content of the food. Instead, we have to
take into account ‘caloric availability’,
which is the amount of energy we can extract from a food, as opposed to the total number of calories in it. Digestion
breaks food into its nutritional building blocks, all of which get moved across
the gut wall into our blood. These
building blocks are, however, just easily
transportable intermediates that need to be metabolised to be converted into usable energy. This process of producing energy, also costs energy.
The two elements of food that have
the biggest influence on calorie availability are protein and fibre. If we zoom out and take a broader view, it
becomes clear that this concept goes far beyond an esoteric piece of nutritional trivia; rather, it explains how many
popular diets work.