Weight.
We’ve been told that weight loss is a simple equation: reduce calories coming in (by eating less) and/or increase calories going out (by exercising more), but the human body is far from simple.
We now know that weight gain is a process driven by hormones, and that it’s what we eat — as well as when we eat — that determines whether the body burns or stores fat.
The type of food you eat, is more important than the calories.
Low calorie diets may result in short term weight loss. However, they also cause hunger and slow down metabolic rate, making it increasingly difficult to lose weight over time. When the diet stops, metabolic rate stays low, which means all the weight (and often more), comes piling back on.
… Sound familiar?
Rather than yo-yo dieting, the goal is to lose weight sustainably, and without constant hunger. To do this, we need to understand what causes weight gain, and hunger, in the first place.
Weight Gain.
When it comes to weight management, the most important hormone is insulin.
Insulin tells the body when to store fat, in fact it’s impossible to gain weight without it. When blood sugar levels increase, insulin is released. It instructs the body to burn sugar for fuel, and convert all excess sugar to fat.
Very high blood sugar levels (spikes), require a large amount of insulin to bring them back down to normal. Large amounts of sugar are converted to fat. If we regularly eat foods that spike blood sugar, insulin levels stay high. The body continues to store fat, leading to weight gain.
When blood sugar is high, insulin tells the body to store the excess sugar as fat.
When blood sugar levels are normal, insulin falls, allowing the body to burn fat instead. Body fat is broken down to be used as fuel, resulting in weight loss. Keeping blood sugar at a steady, healthy level is the key to losing weight.
When insulin is low, body fat is burnt as fuel.
Foods which spike blood sugar don’t keep you full.
High insulin often leads to blood sugar crashes, causing hunger and cravings.
Hunger
Blood sugar spikes are usually followed by blood sugar crashes (where levels fall too low), due to the large amount of insulin released.
This can result in feeling tired, hungry and craving sugar, within only an hour or two from eating.
Blood sugar crashes cause hunger.
Think of your body like a fuel tanker.
High insulin forces the body to burn sugar for fuel (from the small front tank). All excess sugar is stored as body fat causing weight gain (in the large tank at the back). Every couple of hours the small tank runs low, you feel hungry and stop to “refuel”.
Low insulin allows the body to assess body fat. The fuel in this large tank can be burnt for prolonged periods, facilitating weight loss without hunger.
Calories.
Imagine how you feel after eating a Mars bar, and compare that to eating 3 large eggs. Both contain the same number of calories, but which keeps you full for longer?
Eating the Mars bar spikes blood sugar. High insulin switches on sugar burning and fat storage. This is followed by a blood sugar crash, causing hunger and sugar cravings — you’ll likely eat again within a couple of hours. The cycle repeats, making it very difficult to lose weight.
The eggs contain protein and healthy fats, and do not raise blood sugar. Insulin stays low, enabling the body to burn fat. Once energy from the egg has been used, body fat is broken down for fuel. You’ll feel full for longer and find it easier to lose weight.
3 eggs
240 cals
steady blood sugar
full for hours, fat burning.
Mars bar
240 cals
blood sugar spike then crash, fat stored, hungry within hours.
When you choose nutritious foods that also reduce insulin and hunger, it becomes much more difficult to overeat. Keeping insulin low also increases metabolic rate, so your body burns more energy at rest.
What next?
Avoiding blood sugar spikes allows insulin to fall, which tells the body to burn fat.
So, to lose weight, we need to know which foods spike blood sugar.
Although there are some obvious ones (think lollies and chocolate!), some other foods may surprise you!
The science.
Read the high quality evidence linking high insulin and insulin resistance to weight gain.