Are all calories created equal? This is the question that weight loss experts have been exploring for years.
Diets like Keto, Atkins and Dukan are based on the principle that calories are not all the same, and that calories from protein have a different impact on the body than calories from carbohydrates, fat or sugar. Based on this idea, a healthy diet would involve eating more of certain kinds of calories and less of others.
But is there any merit to this approach? Well, when it comes to long-term, sustainable weight loss, the short answer is ‘no’.
Individual people may find these approaches make it easier for them to achieve or maintain a calorie deficit in the short term, and that’s great. But there isn’t strong evidence that this approach is better when you look at sustained weight loss over time.
It’s true that different kinds of food have a different impact on our health. We all know that the nutritional content of broccoli majorly differs from the nutritional value of french fries. And there are many good reasons to eat a varied diet high in fruits, vegetables and fibre.
But when we’re talking specifically about changes in weight, the energy content of food – i.e. the calories – is what counts.
We know that certain foods might make it easier to consume fewer calories. Unsurprisingly, 500 calories of quorn pieces and carrots is a lot more food than 500 calories of chocolate.
It’s also true that we are less efficient at generating energy from proteins, compared to fat or carbs. There are small differences in how we metabolise different nutrients, but within the realm of broadly normal diets these differences aren’t so big that people should fixate on them.
It’s complicated, but if you’re looking for a single metric to assess which foods might help you maintain a healthy weight, then energy density – i.e. the number of calories per 100g – is a good place to start. Broadly speaking, the lower the energy density of our food, the more of it we can eat without gaining excess weight.
So while a regular boiled potato is fairly low in energy density at 79 calories per 100g, that shoots up to a much more high-density 521 calories for ready salted crisps – meaning we can eat more boiled potatoes than crisps!
Real world studies do suggest that low-fat, low-carb and high-protein diets can all have a positive effect on weight loss. The bad news? It doesn’t seem to last, at least not in a meaningful way. Because to be successful in any kind of attempt at weight loss, we need to consume fewer calories than we did before, and we need to stick to this new level long-term.
That’s not to say that everyone should be actively tracking their own calorie intake all the time. This method of ‘calorie counting’ has similar issues to branded diets like Keto, Atkins and Dukan. It requires a lot of effort for the individual and is difficult to sustain.
Weight loss is always going to be about more than just counting calories. Bodyweight is an equilibrium system, so we need to be building habits that are sustainable long term. If we go back to eating the same things we did before, we’ll eventually end up at the same weight.
The key thing is to focus on changes that can be kept up as part of your lifestyle, ensuring that these changes result in an overall reduction in calories.
If a certain diet helps any individual to achieve that long-term calorie deficit, then that’s great! But it’s important to understand exactly why the diet works – it’s not down to any ‘one simple trick’ or to intricate nutritional magic. Ultimately, it’s simply consuming fewer calories over time that makes the difference.
In the end, the success rate of all the complicated diets hitting the headlines generally comes down to one simple thing: controlling calories.