Tallying kcals may be out of fashion – now replaced by modish macros – but when it comes to weight loss, it’s the only strategy that adds up
In my job as a trainer, the question I get asked most frequently (besides whether we can train arms today) is: “Can trending eating plans such as intermittent fasting or the ketogenic diet actually speed up my weight loss?” The simple answer is yes. But if they all work, why are there so many options, and why is the country in the grip of an obesity epidemic? This is equally easy to explain: the results are almost always temporary 1 .
Many people assume that there must be a complex biochemical reason why these diets work, but the reality is far more mundane. It’s all just maths: simple addition and subtraction, the sort you can do in your head. If we consider intermittent fasting, all that you’re doing by creating arbitrary boundaries around the times you can eat is limiting the amount of calories you consume over a given period of time.
Similarly, by cutting out a food group, or even an entire macro nutrient (in the 1980s, it was fat; in the 1990s, the enemy was carbs; more recently, it’s meat and dairy), you end up reducing your caloric intake. If your activity levels stay consistent, then the resulting calorie deficit will translate into weight loss. Over time, however, you inevitably find a replacement food from within your “permitted” group, and the deficit is nullified. For example, if you remove the roast potatoes from Sunday lunch because “carbs are bad”, you will consume fewer calories and lose weight. When, after a few weeks, you realise you’re still hungry on Sunday afternoon and replace the potatoes with extra beef (after all, “protein is good”, right?), the weight piles back on.
The 16:8 diet is foiled in a similar way. Not eating after 6pm is an easy way to cut out a late-night snack habit and reduce overall calorie consumption across the day. However, if your solution to that hunger is to get your evening’s worth of snacks crammed in by 5.55pm, the deficit will be reversed and that weight will go back on again – even though you’re following the rules 2 . When a Journal of Nutrition, Health and Aging study compared intermittent fasting to caloric restriction, subjects lost an average of 1.25kg a month through the latter, while the fasters only shed 473g 3 .
Let me be clear: there is more to good health than calories. A low-calorie diet that lacks the proper balance of vitamins, minerals, fibre and macronutrients will do little to help you feel great and train hard. Yet, once you cut through the fancy marketing spiel and the celebrity endorsed books, it becomes clear that the relationship between food and weight loss is still defined by simple calories. It’s energy in versus energy out.
The most successful eating plan is the one you can stick to. If being vegan works for you, embrace it. If paleo appeals, have a butcher’s at the meat counter. But, if losing weight is your primary goal, for goodness sake don’t pretend that your dinner can tell the difference between 6pm and 10pm. It’s a numbers game, plain and simple. Start counting.
“It’s all just maths – the sort of addition and subtraction you can do in your head”
IF YOU WANT A FOOD PLAN TO DELIVER, DO THE MATHS