The Difference Between Intermittent Fasting and Calorie Restriction
This is one of the most common questions I asked. Many Personal Trainers and calories in/calories out advocates agree that fasting works, but only because it restricts calories. This thinking disregards a lot of hormonal and metabolic changes that happen in the body when we fast compared to when we restrict calories.
Why ‘Eat Less, Do More’ Doesn’t work
The strategy of constant caloric restriction is the most common dietary approach recommended by nutritional authorities for weight loss. It looks like it’s here to stay – Public Health England just announced Britain’s new diet, and guess what? It’s calorie restriction 2.0!
Once again the British Government has missed the mark on trying to tackle the obesity epidemic???. • @publichealthengland has advised the UK to cut their calories to: 400cals for Breakfast, 600cals for Lunch and 600 Cals for Dinner. • Essentially this is nothing new, all they are doing is telling us to eat less – really helpful! I wonder how much money was spent on this campaign!? • In my opinion, having calorie counting as the basis of your weight loss tactics is going to lead to poor food choices, lack of nutrients and hunger. • A calorie is the measure of the amount of energy in a given food, this takes no account how the food affects hormones, hunger levels or the number of micronutrients it may or may not have. • You want to create the right hormonal environment in the body so that you are burning fat, promoting stable blood sugar levels and feeling satiated after you eat. Focusing on eating nutrient dense foods, cooked from scratch is a way of doing this. • If you focus purely on trying to restrict calories, you may see some weight loss results in the short term, but it cannot be sustained long-term. You can start to slow your metabolism down as your body starts to try and conserve energy. • You are likely to lose muscle mass, which in turn can make it harder to lose weight in the future because your resting energy expenditure is lower than it was before. (The more muscle you have the more fat you will burn at rest!). • The campaign has put a big focus on getting food sellers and manufacturers to cut calories in their products by 20% by 2024, with big businesses that fail to make progress set to be named and shamed. • The fact of the matter is if you want to reach optimum health and be in a healthy weight range, you SHOULD NOT eat food made by big food manufacturers and fast food chains. • They have missed the mark entirely, what they should be doing is encouraging people to cook from scratch with fresh ingredients and less processed food. • DON’T EAT LESS – EAT BETTER. • Leave your thoughts and comments below??!
There is now calorie information everywhere, and there are calorie counting apps and hundreds of calorie counting books. Even with all this, success in the long term is rare.
The classic ‘Eat Less, Move More’ approach endorsed by all the nutritional authorities does work, in the short term. However, long-term it is unsustainable. What happens when you exercise more? You get hungrier! This is precisely how it should be; your hunger levels should fluctuate depending on your energy expenditure.
When you calorie restrict your Basal Metabolic Rate (BMR) drops (the energy needed to keep your body functioning) – sometimes irreversibly. As your metabolism decreases, weight loss plateaus. Caloric reduction forces your body to slow down. Once you go back to eating regularly what happens? Weight gain, and it’s often worse than it was before.
This metabolic slowdown has been scientifically proven for over 50 years. In the 1950s Dr. Ancel Key’s famous Minnesota Starvation Study placed volunteers on a ‘semi-starvation’ diet of 1500 calories per day. This represented a 30% caloric reduction from their previous diet. In response, their basal metabolic rate dropped about 30%. They felt cold, tired, and hungry. When they resumed their typical diet, all their weight came right back.
Caloric restriction diets only work in the short-term, before basal metabolism falls in response. Daily calorie restriction fails because it puts you into a metabolic slowdown. It’s pretty much guaranteed.
The secret to long-term weight loss is to maintain your basal metabolism. What has been shown time and time again to be an efficient way to lose fat without slowing the metabolism? Intermittent Fasting.
Intermittent Fasting is the answer
Fasting triggers numerous hormonal adaptations that do NOT happen with simple calorie restriction. Insulin levels lower, helping prevent insulin resistance. Norepinephrine rises, keeping metabolism high. Growth hormone increases, maintaining lean mass.
Why does it work so well?
Why is this? Imagine back when we were hunter-gatherers. There were periods when food was scarce, if our bodies were to slow down and go into “starvation mode” then we would become lethargic, with no energy to go out and catch out next meal – we would start tapping into muscle to use as energy and eventually die.
The human species would have become extinct long ago if our bodies slow down each time we didn’t eat for a few hours.
In fact, fasting creates the right hormonal environment in the body to start using our stored food – body fat. Basal metabolism stays high, and instead, we change fuel sources from food to stored food (or body fat) which is precisely why it’s there. This is an entirely natural process, but the modern environment doesn’t encourage the right hormonal conditions to start using fat.
During fasting, we first burn glycogen stored in the liver. When that is depleted, we use body fat. Which we have a lot of! Since there is plenty of fuel, there is no reason for basal metabolism to drop. And that’s the difference between long-term weight loss and a lifetime of yo-yo dieting.
I can hear many of you thinking – but I have a low body fat, I don’t have any fat to tap into?!
Let me put this into perspective, I have roughly 8% body fat which is very low compared to the average guy. That 8% equates to roughly 8kg of fat spread-out throughout my body.
Roughly 0.5kg of fat equates to roughly 3500 calories worth of energy, so if we do the maths I have roughly 60,000 calories worth of energy to tap into!
So even for someone like me with a low body fat percentage, there is still ample reserves of stored energy
So to sum it up…
Fasting has been used throughout human history as an effective method of controlling obesity, increasing energy and cleansing the body. By contrast, the portion control strategy of daily caloric restriction has only been recommended for the last 50 years with almost universal failure.
We’ve known for a long time that dieting makes you hungrier. It’s not a matter of willpower — it’s a hormonal fact of life — ghrelin levels (the hunger hormone) increase and you are hungrier. However, fasting does not increase hunger. This is why it becomes a way of life for so many people.
Calorie restriction diets ignore the biological principle of homeostasis — the body’s ability to adapt to changing environments.
The same applies to weight loss. Your body adapts to a constant calorie restriction by slowing metabolism.
Successful weight loss requires something that creates the right environment for your body to use it’s stored energy. Once you are burning body fat, you will lose weight, have more energy and feel less hungry – it’s a game changer!