The Problem With Drinking Calories
Before writing the rest of this principle, please let me take pause to restate that these are principles, not dogmatic rules. I do not want to communicate that 100% adherence to them is a necessity, or even recommended. They are intended to be followed as general principles, most of the time.
Drinking calories in the context of our physiological evolution is a very, very minor component of the human diet. After infant-hood, the availability of calorie-containing beverages is scarce. Some tribes have been noted to drink blood, which has a very small amount of calories, and some segments of hunter-gatherers drink animal milk. This is very different from the abundance of calorie-dense, often nutrient sparse drinks that are available to us today. Everything from 20oz lattes with sugar syrup, to fizzy drinks, sports drinks, energy drinks and even “healthier” options such as fruit juices and smoothies are available incredibly easily.
The problem with drinking calories is threefold.
Firstly, there is the obvious problem that our satiety signals work far better when we eat solid food than they do when we drink our calories. The slower digestion and thus absorption rates necessitated by the required mechanical breakdown of solid food cause a far slower process, even for exactly the same foods, than when that mechanical breakdown is done by a blender. Rapid and easy digestion and absorption lead to greater swings in blood sugar, insulin, blood fats and hunger. This is the antithesis of the stable state that is more conducive to metabolic health and good body composition.
Secondly, we have the actual nutritional composition of the calories being drunk. Generally, calories you drink are likely to be low in fibre, protein and micronutrients, and high in sugar. This flys in the face of all the benefits of the preceding principles of eating only meals, stopping when satisfied and basing your diet on whole food, and thus negates all the benefits described prior.
I may hear some of you now protesting that your morning smoothie is actually a meal and is made from whole foods. I grant you that this is true, but still, I will now rant about smoothies. Let’s take for example a smoothie recipe that boasts 1 whole banana, 1 apple, 1 kiwi, 1 handful of blueberries. Compared to actually eating these fruits the digestion, absorption and resulting impact on your physiology will be much less desirable. With a rapid rise in blood sugar and fructose intake into the liver, a greater inhibition of fat metabolism, a rise in insulin and a move towards triglyceride formation in the liver is all far greater than the exact same metrics after eating the solid fruit. There is also the issue with satiety, which will also be less long-lived than it would have been had you eaten the fruit.
Thirdly, there is the issue of there being no protein and no vegetable in that meal. Adding powdered protein will help to mitigate this, but again the digestion is far more rapid and in the case of whey will lead to a quite pronounced insulin spike. Again, slower digestion and absorption is generally more desirable. Veg can, of course, be added to smoothies, if not the sole constituent. This is far superior to fruit-based smoothies, and may well be the exception to the rule.
The exceptions to the rule…
There are some situations where I recommend blending and drinking highly nutritious calories, worth noting here as exceptions to the principle. Mainly, gaining muscle requires overconsumption of calories above your maintenance intake. One thing that will consistently be reported by those who have endeavoured to gain appreciable amounts of muscle, is that the eating is one of the hardest parts. Especially if you are eating nutrient-dense whole foods and protein at every meal, you will see that hunger is dulled and motivation to keep eating is absent, leading you to fall short of the excessive intake required for appreciable muscle gain. (Incidentally, this perspective illustrates just how well the prior principles work to avoid overeating – when you actually try to overeat it is very difficult).
In this case, I would have clients consume shakes made up of protein, MCT oil and depending on the situation, maybe oats or flaked quinoa, and fruit like berries. These shakes would be taken in between meals as a tactic that facilitates extra calorie intake due to the minimal impact on satiety and the relative calorie density of the shake. Again, this illustrates exactly why it is not a great idea if GAINING weight is not your goal.
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