Chances are someone has recommended a diet to you recently, because it works well for them and they say it will work well for you, too. But how do you know if it really will?
Here's the secret: most diets work in almost exactly the same way.
Let's rewind a little. People go on diets all the time, and the most popular reason for doing so is to lose weight. That's what this post is about: weight-loss diets. This post will not address diets for disease management (such as diabetes or cancer) nor will it discuss diets for muscle-building or any other reason. This is a post about weight loss.
If you want to lose weight, you must spend more energy than you consume. This sounds so simple, and yet in reality it is quite difficult for many reasons. One of these reasons is that we don't have an accurate and handy way of measuring exactly how much energy is in our food, how much energy we can actually digest and absorb from that food, or how much energy we really spend every day. So unless you live in a lab, your weight loss calculations will be finely-tuned educated guesses.
Let's get down to diets. Kenny at the gym swears that everyone should be on keto (a ketogenic diet; an extreme version of a low-carbohydrate, high-fat diet), Jessica at work is on a raw vegan diet, Miranda is on the Mediterranean diet, and John does intermittent fasting (IF). So which diet should you chose?
All of these diets are exactly the same but completely different. They involve very different food choices or eating schedules, but they work because they enable the person on the diet to be in a "calorie deficit" - they are burning more calories than they consume. In other words, the person is eating slightly less that what is needed for their body to function, so the body turns to stored fat as a fuel source.
The ketogenic diet is highly restrictive, in that carbohydrate-rich foods (such as fruit, grains, beans, legumes, starchy vegetables, cakes, chocolate, lollies, joy...) are limited to as little as possible. Foods rich in protein and fat are favoured instead. Restricting the type of foods a person can consume usually leads to that person eating fewer calories over the course of the day, as there is simply less food to choose from, and because protein and fat keep you feeling fuller for longer (compared with carbohydrates).
As well as that, sugary foods tend to be quite addictive and are very easy to over-eat. We are much less likely to over-eat salmon, avocado, and spinach than we are to over-eat biscuits, chocolate, or other sweet foods. Weight-loss on a ketogenic diet occurs because the person ends up eating fewer calories than they use. There may be other benefits to a ketogenic diet, but the laws of thermodynamics remain the same: weight loss occurs only in a calorie deficit.
Intermittent fasting (IF) works in a similar manner.
There are two common forms of IF. One is based on non-restricted food choices but restricts the daily "eating window." This usually means that a person will only eat between 11am and 6pm, for example. Times will vary from person to person. As most people can only fit a certain amount of food into their stomach at each meal, limiting the eating window means that the calories consumed during the day are lower overall.
The second form of IF is one or more days per week of either complete fasting (not eating) or drastically reduced calories. Normal, non-restricted eating occurs on non-fasting days. This leads to a lower quantity of calories consumed over the course of the week, and the weekly calorie deficit leads to gradual weight loss.
Most diets restrict calorie intake in some way; either by restricting food choices, restricting food quantity, prioritising high-nutrient/low-calorie foods, or restricting the time allocated to eating.
The trick is to find the diet that simply feels like the least effort for you. For someone who loves "bulletproof" coffee, butter, and bacon, but doesn't have much of a sweet tooth, a low carb / high fat or ketogenic diet won't test their willpower too much.
For those who love all types of food but are busy people and often forget to eat breakfast or lunch, or have a couple of low-activity days during the week, intermittent fasting should be fairly easy as long as you don't mind the feeling of hunger, and as long as the restriction doesn't lead to binge-eating.
If you have a big appetite and get hungry often, prioritise foods that are high in satiating nutrients such as fibre and protein, but low in calories. Good choices include unprocessed whole foods such as vegetables, beans, legumes, and seeds. This will lead to feeling full but consuming fewer calories.
If you love animals, don't eat them. Apart from the ethical and moral issues, animal-based foods tend to be high in calories and saturated fats, and are often very processed. Choosing plantbased foods is a good start. Just beware of the new wave of delicious vegan junk foods that are also highly processed and high in calories!
Just remember, you'll need a little balance and a little healthy restriction. We can't live on coconut icecream and beer, nor is it healthy to go fat-free. Good fats (think Omega-3) are essential for our brains and hearts.
Given that the basic rule is to achieve a calorie deficit, any or all of these diets could work for you. Similarly, what works for one person will not necessarily work for another. Choose a way of eating that includes plenty of protein, a little fat, an appropriate amount of carbs, and helps you to achieve a calorie deficit without too much effort. A good dietary pattern should be one that you can maintain long-term.