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There’s a lot of hoo-ha about calorie content in food in social media and in the popular press at the moment. Since April 2022, UK restaurants with over 250 employees are required by law to list the calorie content of each item on their menus. Some people object on the grounds that knowing the calorie content of what they are about to order puts them off enjoying the meal. Others say most people will ignore the calorie listing so what is the point of including the figures? People recovering from eating disorders such as anorexia and bulimia say they have panic attacks when they see the calorie figures. And restaurant owners say that adding calories to their menus is extra work and based on an inexact science. How do you calculate the calorie content of a takeaway fish-and-chips meal when the size of the fish is variable and the portion of chips is based on how generous the proprietor is feeling at the time of service?

Then we see a headline such as this:

Daily Mail, June 21, 2022.

Megan Rossi, known affectionately as the Gut Health doctor or Gut Guru, opines that the number of calories listed in standard portions of food is not the same as the number of calories encountered and consumed by the body. The way calories are measured by those back in the food science labs used to be done by burning the food and observing the resulting rise in the temperature of water that is directly heated by the combustion process. Recall that a Calorie (upper-case C) is the amount of energy required to raise the temperature of 1 kg of water by 1 degree Celsius. And that’s another source of confusion. When we speak about food (“large”) calories, we are actually talking about Calories where 1 Calorie (1 kcal) is 1,000 “small” calories. A small calorie is the amount of energy required to raise the temperature of 1 gm of water by 1 degree Celsius. So if you are chomping on a standard 51 gm Mars bar containing “229 calories”, you are actually consuming 229 Calories which equates to 229,000 small calories! Confused? Yep, but “229 Calories” doesn’t sound as bad as 229,000 calories, does it?

Back to how the labs measure the calorie content of food – those figures we now see on the packaging of products bought in a food store. These days, we know the chemical composition of foodstuff and, in particular, the energy-containing nutrients such as fat, carbohydrate, alcohol, and protein. Thus, food scientists can make use of a set of standard energy values, Calories per gram, for each type of nutrient and add up the total amount of energy available per unit weight or volume of the product. The system, based on the work of Dr Wilbur Atwater, an American chemist active during the years 1868–1904, is not without controversy but has remained the mainstay of calorific assessment techniques for nutritional purposes.

Let us also return to Megan Rossi’s point – counting calories is a waste of time. Is she right? Maybe just a little bit but the headline does not tell the whole story. It has long been held that in order to lose weight we must control our calorie intake as related to our daily need for calories to supply fuel to keep us alive. “If you consume more calories than the body requires, unused calories will be deposited and stored as fat. If you consume fewer calories than the body requires, the body will draw on the store of unused calories, if available, and you will lose weight.” So reads the mantra. And it’s true. An excess of unused calories results in deposits of calorie storage around the body – fat. But, here’s the first problem. How many calories do we need each day to maintain a weight equilibrium? There are as many answers here as there are spots on a leopard! Are you male or female, or in-between? What age are you? Do you exercise regularly? What type of exercise – cardio, muscle, aerobic – and at what level? What is your Basal Metabolic Rate (the rate at which you burn calories to fuel basic bodily functions when either lying in bed or otherwise in a resting state)? How efficiently does your metabolic system convert calories into energy that is used by the muscles, heart, brain, lungs, liver, and all the other parts of the body that require energy to function? What is the ambient temperature in which you exist – are you warm, cold, or comfortable – and how does this ambient temperature change throughout a 24-hour period? Do you eat regularly, with or without snacks in-between? And so on. If we look up how many calories we need per day to neither gain nor lose weight (called the maintenance calorie level), how much credence can we place on a single figure? For example, in my case – male, aged 80 – the NHS website advises 2,500 calories/day based just on my sex whereas the VeryWellFit website takes into account my sex, height, weight, and age and, via a magic formula, comes up with 1,632 calories/day. That’s one helluva difference!

A well-known rule of thumb regarding weight loss is that a daily calorie deficit of 500 calories (500 calories fewer per day than your daily maintenance level) will add up to a calorie deficit of 3,500 per week which, in turn, will result in a weight loss of 1 lb. (In metric terms, this rule becomes a 555-calorie deficit per day results in 0.5 kg weight loss over a week.) In the past, I have assessed the accuracy of this rule. In 2008, just after retiring from a busy career, I needed to lose weight and embarked on a strict calorie-controlled diet combined with exercise and, as per my engineering training, I kept detailed records of my calorie intake plus calorie burn per day. I religiously calculated the calorific values of food and drink consumed at home. In restaurants, I estimated portion sizes and later calculated calorie values. On the treadmill, I entered my weight and age and used the resulting calorie-burn values. Out walking, I used calorie-burn values based on the treadmill values. In short, I tried my best to use inexact figures from dubious sources but over a period of a few months, the weight loss worked out as planned. On average, the weight loss I experienced did equate to approximately 1 lb per 3,500 calorie deficit per week and, over a period of ten months, my weight dropped by around 44 lbs (20 kg) i.e., 1.1 lb (0.5 kg)/week on average. The weight loss versus time graph was not linear (I didn’t expect it to be) but I was happy with the result and, more importantly, developed a better understanding of what particular foods and drinks contributed to a successful weight-loss program. And this, surely, is the point about calorie awareness? I know now that a handful of nuts or a fistful of crisps while in the pub drinking a pint of beer is definitely not a good thing to do. So, I might reduce the pint to half a pint, or drink fizzy water instead, and shun the proffered nuts and crisps. Similarly, in a restaurant, I’ll gravitate more towards a salad followed by soup rather than the stuffed jalapeño peppers followed by a double cheeseburger with fries. But, I draw the line at ice cream! A man needs a decent portion of ice cream once a week. And chocolate!

Megan Rossi is a self-proclaimed dietician and nutrition expert and, as such, she needs an angle to get herself into the world of celebrity health experts. The Atkins diet, and its successor, Keto, is based on controlled carbs. Another fashionable diet advocates intermittent fasting. Then we’ve got a variety of diets based on various techniques: low protein, vegan or vegetarian, Mediterranean foods, liquid plus solids (Slimfast styles), South Beach and Dukan (low-carb, high protein), and many more. Now Rossi says calorie counting doesn’t work for a variety of reasons and you should base your diet on plants – vegetables, fruit, pulses (peas, beans, lentils, etc.), herbs, and spices. I am in broad agreement with her conclusion but not with her basic assertion that calorie counting is a waste of time. It depends on how you measure success. I accept that calorie counting is a highly-suspect science – how are the calories measured and with what accuracy?; does the body process every consumed calorie by turning it into either useful energy or depositing it as fat or even expelling it unused in the body’s waste?; can we really assume that the body needs the same fixed amount of maintenance calories each day and how is this value calculated?; what really constitutes a balanced diet – is it just calories?; what about proteins, vitamins, minerals, fibre, and liquids?; and so on.

It’s complicated and very few of us have the time or inclination to read and understand any of the health-expert books or cook from the health-conscious cookery books. We just want to get on with our lives and remain reasonably healthy, including our weight. I contend that although calorie counting is a very inexact science, it’s all we’ve got as a way of maintaining a healthy diet. Calorie counting coupled with low-fat awareness (the two are often the same) will naturally force you into eating healthy foods such as vegetables, fruit, salad (a mix of vegetables and fruit), white meat (fish and chicken) if not a vegan, pulses, nuts,… and drinking low-calorie liquids and, in the end, isn’t that the ultimate aim of all these health experts?

Increasing our awareness of foods and liquids that contribute to obesity is what counts and counting calories contributes significantly to this awareness. Contrary to the Daily Mail’s headline, calorie counting is not a waste of time. It’s fundamental to our ability to maintain a healthy weight through healthy eating and drinking. Don’t knock it.