Sometimes it happens during a workout, sometimes it happens at work— fatigue, loss of focus, the shakes, grumpiness, limbs like rubber-bound bricks, all accompanied by a dull headache. It’s time to stop running, time for a cup of Joe or a handful of sugar. You know the feeling: the bonk.

How - you wonder - did this happen? To put it simply, all the energy you have comes from the food you eat. Period. So look at what you ate.

Here’s how it works: mainly carbohydrates and fat are burned to produce energy (protein is burned only when there isn’t enough of the former two). Once in your body, these food molecules are stripped of their energy and converted into glucose, which is the main cellular energy source. It’s like gas in a sputtering Volkswagen.

A host of enzymes and vitamins are required for this energy transfer process to occur, in particular vitamins B₁, B₂, B₃, B₅ and B₆ which are largely found in animal proteins. These essential enzymes, meanwhile, are also formed from proteins. So as we can see, an energy-supportive diet needs to contain complex carbohydrates, quality proteins, and healthy fats. Here’s where to start.