A new study reported in the New Scientist has revealed that the number of calories reported on the pack may be as much as 25 per cent ‘out’ compared to the food’s actual energy-providing value. Enough to scupper any diet, in other words – and definitely enough to make you put on weight.

While it’s broadly true that maintaining a healthy weight is mainly a question of calories in versus calories out, scientists are now arguing that the methods used to calculate calorie contents are out of date (over 100 years out of date, in fact) and that they don’t take into account that digestion – from chewing food to moving it through the gut and chemically breaking it down along the way – takes a different amount of energy for different foods.

In the case of the brownie versus the cereal bar, the label will overestimate the calories derived from the fibre- and protein-packed bar, perhaps by enough to make it lower in calories than its cake-y counterpart. Another thing to consider is that the brownie is much softer than the cereal bar, a factor that has been proven to lower the energy cost of digestion. So giving your body lots of easy-to-eat, soft food could lead to putting on more weight than if you ate a greater calories’ worth of harder textured food (like fruit, nuts and seeds).

But no matter what the studies tell us, the matter of healthy eating – and healthy weight maintenance – always boils down to the same thing. Wholesome, fresh, processed-as-little-as-possible foods will forever do your body more favours than their refined, over-processed counterparts; but on the other hand, if you really fancy the brownie, you should have it.

Just make sure you’re eating it because it’s a delicious, squidgy treat, not because you think it’s the healthy option.