“The trouble with any diet is that it’s not necessarily practical to live your life constantly restricting or counting calories. Sometimes this can lead to us thinking of foods as ‘good’ and ‘bad’, when really it should be all about balance and, importantly, enjoying food.”
Pigott points out that over-simplifying the relationship between diet and exercise to focus solely on calories can mean we become tempted to only eat the foods that we like, rather than truly thinking about what would benefit our bodies.
“For example, we could think it’s a great idea to eat six chocolate bars a day and achieve a negative energy balance [through exercise], but put ourselves at risk of gut problems, anaemia and nutrient malnutrition,” she says.
Dr Sally Norton, a consultant who specialises in weight loss, says scientifically, attempting to match your calorie intake and calories burned during exercise is impossible to do accurately, anyway.
“To work out a calorie count, manufacturers will calculate the amount of fat, protein and carbohydrate in a meal or snack,” she explains.
“They will use the figures that 1g fat provides 9kcals, and 1g of protein or carb gives us 4kcals. However, these figures are calculated by taking these foodstuffs and burning them over a Bunsen burner in a lab to see how much energy they generated.
“This doesn’t necessarily equate to the energy they produce when they are in our body.”
She adds that not all the food we consume is actually broken down completely in our bodies, making some calorie counts unreliable.
“Without putting too fine a point on it, some passes through relatively unscathed – particularly food that hasn’t been overly processed before it reaches us,” she says.
“Our digestive process is incredibly complex – I have worked in this field for 20 years and still don’t come close to understanding it. So to equate its energy-extracting process with that of a basic scientific experiment in a sterile lab is completely over-simplistic.”
According to the NHS, an average man needs around 2,500kcal (10,500kJ) a day to maintain a healthy body weight, while a woman needs around 2,000kcal (8,400kJ) a day.