Weight loss is simple, right? You just burn more calories, through exercise and daily activity, than you take in through food.
WRONG! I’ve been explaining to my clients for years that there’s a lot more to it than that!
For starters, we don’t necessarily absorb all of the calories contained in the foods we eat. For example, up to 60% of the starch calories in legumes (dried peas, beans and lentils) are in the form of resistant starch which is not absorbed from our digestive tract.
Now, weight loss researchers have discovered another way in which the real world just refuses to conform to the ‘calorie in, calorie out’ model:
A diet with a low glycaemic index (GI) maintains weight loss better than a high-GI diet, even when the two types of diet have exactly the same number of calories!
GI refers to how quickly the carbohydrate in foods is broken down into sugars and absorbed into the bloodstream. High-GI foods cause our blood glucose level to surge after a meal, while low-GI foods maintain a much steadier blood glucose level, which delays the onset of hunger after a meal, allowing us to voluntarily eat less.
The aim of this new study, published in the Journal of the American Medical Association, was to determine which kind of diet – low-fat, low-GI or low-carbohydrate – was the best at maintaining weight loss.
It’s well known that the overwhelming majority – at least 80%, and probably more – of people who intentionally lose weight by ‘going on a diet’ regain that lost weight within 1 year.
Although part of the explanation for this weight regain is that over time, most people lose motivation and revert to their old way of eating, there is another important contributing factor: metabolism declines after weight loss, causing lower energy expenditure (the rate at which calories are burned).
Weight loss also tends to increase appetite, making people want to eat more.
To investigate the effect of different types of diet on energy expenditure and weight regain, the researchers recruited 32 overweight adults (of whom 21 completed the study), aged 18-40, and put them on a low-calorie diet until they lost 10-15% of their initial body weight.
They then calculated – using indirect calorimetry, which measures how much oxygen an individual consumes at rest – how many calories each participant would require daily in order to maintain their new, lower weight.
This allowed the research team to construct diets in each of the 3 test categories, that had exactly that number of calories.
Every participant then followed each of the 3 types of diet, for a month at a time, in random order. This study design allowed the researchers to examine in detail, how each diet affected the participants’ metabolisms.
Here are the characteristics of the 3 test diets:
- The low-fat diet comprised of 60% of daily calories from carbohydrates, 20% from fat and 20% from protein. It was rich in whole grain products and a variety of fruits and vegetables, and had a high glycaemic load (glycaemic load, or GL, is calculated thus: the food’s GI x grams of available carbohydrate in the food/100).
- The low-glycaemic index diet supplied 40% of daily calories from carbohydrates, 40% from fat and 20% from protein. The glycaemic load of this diet was low compared to the low-fat diet, because much of the grain products and starchy vegetables were replaced with low-GI vegetables, legumes, and fruits.
- The low-carbohydrate diet was modelled on the Atkins diet, and comprised of 10% of daily calories from carbohydrates, 60% from fat and 30% from protein.
So, what did they find?
1) All the different test diets resulted in a decrease in energy expenditure; no surprise, since when people weigh less, they use less calories to maintain their bodies. But the low-fat, high-GI diet resulted in the greatest decrease in energy expenditure. And this, of course, means a higher likelihood of regaining weight.
2) Levels of the ‘appetite hormone’ leptin were highest when participants were on the low-fat diet. This is an indicator of leptin resistance (in the same way that insulin levels are higher in type 2 diabetics, who are insulin resistant). Leptin resistance is strongly associated with obesity, so a diet that causes leptin resistance is very likely to cause weight regain.
3) Production of cortisol, a stress hormone associated with fat gain, insulin resistance, and cardiovascular disease, rose when participants ate a low-carbohydrate diet.
4) C-reactive protein, a marker of inflammation associated with higher risk of cardiovascular disease, cancer and many other diseases, was highest on the low-carbohydrate diet.
Now, it’s important to note here that the low-carbohydrate diet resulted in the least decrease in energy expenditure and the lowest levels of leptin, both of which are favourable to weight loss.
However, the researchers concluded that these beneficial effects are offset by the harmful effects of higher cortisol and C-reactive protein levels.
Their conclusion: a diet that restricts refined carbohydrates and emphasises plant foods with low glycaemic load, is the best for protecting yourself from deadly diseases while avoiding weight regain.
They also noted that this dietary pattern is much easier to maintain over the long run, than either a low-fat diet, or a severely carbohydrate-restriced diet such as the ones they used in their study.
I’ve been recommending a low-glycaemic load diet – based on non-starchy vegetables, legumes, berries and other low-GI fruits, and nuts and seeds – to my clients for weight loss and weight maintenance, for years!
This eating pattern is delicious, satisfying to your appetite, increases vitality and stamina, and is associated with profound protection against many different types of cancer, cardiovascular disease, type 2 diabetes, stroke and autoimmune diseases, just to name a few.
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