Fish and chips
Fish and chips, tasty but dirty?

We’ve all had it before, there’s always one person in the gym who is convinced that the only way to add any muscle is to consume a massive calorie surplus, the contents of which doesn’t really matter.

Don’t get me wrong a surplus of calories is important but only when you’re getting these calories from nutrient dense, healthy foods.

There are two reasons as to why ‘dirty bulking’ is detrimental to your muscle growth potential and overall body composition.

Junk food = bad food

‘Bulking’ during the winter that consists of eating shed loads of junk food will increase the numbers on the scales, but a large % of the added weight on the scales will be added body fat.

This much is clear and it creates an obvious disadvantage because although you look better on the scales, do you really look better on the beach now your body is riddled with extra fat stores and your abs are nothing but a distant memory? – No-one likes looking soft and puffy!

‘It was all worth it because dirty bulking helped me increase my muscle gains, which means I’ll look better when I diet down.’

Just assuming for a second that you successfully diet down and don’t lose all your hard earned muscle (which is actually quite hard to do) did the dirty bulk actually help to increase muscle growth? Not necessarily…


Dirty bulking decreases insulin resistance which can hinder muscle growth potential.

So dirty bulking increases your body fat %; this much is obvious but what isn’t as obvious is the effect that eating all this junk food has on your insulin; more specifically your insulin sensitivity.

For optimal body composition and to maintain and indeed build muscle you need to be in control of your insulin. Eating large amounts of junk food that is high in sugar, or just by eating large amounts of high G.I carbohydrates with little regard to how it affects your insulin will result in a decrease in your insulin sensitivity.

If insulin sensitivity decreases it can actually impede muscle growth. Insulin is actually a signalling hormone for both muscle and fat cells to utilize amino acids and glucose. Ideally, insulin-sensitive muscle cells will readily absorb glucose and amino acids when insulin “signals” them to open. However, chronic exposure to junk food means insulin levels are consistently high, and this can desensitize muscle cells to insulin’s signalling effects.

Why is this process so important?

If muscle cells become less sensitive to insulin then their ability to absorb glucose and amino acids decreases. This means there’s less amino acids absorbed into muscle cells and available to be utilised for protein synthesis which is an extremely important process required for muscle growth.

If your muscles cells are less sensitive to insulin then they will absorb less amino acids – the very things that are needed for muscle growth.

So not only does eating junk food make you fat, which softens your muscles, hides your six pack and takes weeks of dieting down to get rid of, it also reduces your muscle building capacity.

Take home points…

  • Just don’t get too fat. Even when ‘bulking’ don’t use this as an excuse to bombard your body with junk food.
  • Keep body fat within a certain range at all times.
  • The ideal range is different for different people, depending on insulin sensitivity and other individual factors. If you exceed this range, you’ll know it. More of the weight you put on will be fat, gains will slow down, the pump you get during training will be reduced, and you just won’t have that same degree of muscle fullness. It’s obviously best to avoid this in the first place by eating smart and avoiding these ‘dirty bulks’ in the first place.
  • Remember, you can’t out train a bad diet. Get to the gym and work out, then get home and work in.