There is no standardised definition of bulking and cutting. Bulking involves eating more calories than you need, in order to put on weight, then building muscle via resistance training. Cutting involves eating fewer calories than you burn (and probably doing more cardio) in order to lose the fat. The theory is that you put on extra muscle and fat, but then lose the fat to look lean and shredded.
But does this work and is it a good idea? We ask the experts.
Does more food equal more muscle?
Muscles are made of protein, so eating extra protein should lead to bigger muscles, right? Sort of… but not quite.
When you exercise, you damage muscle fibres, which is a good thing. After exercise, your body repairs these fibres by fusing old and new protein strands together, making them stronger and sometimes bigger. Muscle growth occurs when the rate of protein synthesised into muscle is greater than the amount of muscle protein breakdown.
To increase muscle mass, you must “eat more calories than needed to maintain your body weight”, says personal trainer Scott Laidler. "A high proportion of your extra calories should come from foods containing protein, which will give you the necessary amino acids to build muscle mass. Without protein, you will just gain fat and little muscle", he continues. But there is a limit.
It's not as simple as protein equals muscle. "There is a genetic limitation to how much muscle mass you can put on over a given time, no matter how much you exercise and eat protein", says weight loss coach and personal trainer, Dr Aishah Muhammad. So if you eat too much, you'll just get fatter.
It’s not difficult to eat the amount of protein you need for muscle growth. The UK National Diet and Nutrition Survey reveals that the average amount of protein eaten by a 19-64-year-old man is 87.4g per day and woman 66.6g – much more than the NHS recommendation of 55.5g for men and 45g for women depending on body mass and physical exertion.
Can you eat too much protein?
In 2016, BBC Three reported on a man who was hospitalised after trying to 'bulk up'. He had kidney stones, which he believed were likely to be caused by eating too much protein. He said his body couldn't process the protein and so turned it into calcified deposits in his kidneys.
The NHS links a high-protein, low-fibre diet to recurring kidney stones. The risks associated with a high-protein diet are greater for people with a pre-existing health condition, and if you have kidney or liver damage you should consult a doctor before making changes to your diet.
Back in the 1960s and '70s, when bulking first became a phenomenon, body builders relied on nutrient-dense, natural foods such as steak, milk and eggs. Nowadays, protein is available as shakes, bars and capsules, making it easy to consume vast amounts of it with additional sugar and calories without getting full.
If you want to take a protein supplement, British Dietetic Association clinical and sports dietitian Rick Miller suggests sticking to the recommended serving size and never taking more than is needed.
Can you lose fat without losing muscle?
It’s pretty tough to lose as much fat as you want to while retaining muscle when ‘cutting’.
Years ago, scientists found that a pound of fat contains 3,500 calories of energy. However, burning one pound of body fat isn’t as simple as reducing your calories by that amount – your body loves to burn muscle too.
Scott Laidler learned this from his own journey when he first started out in fitness. He said, “When I cut I took my calories too low and in the process worked off a lot of the muscle mass that I had gained. The phases would cross over for a few weeks, where I would look and feel good, but I wanted to be lean and muscular all year round. It really wasn’t satisfying.”
Bulking and cutting can affect your athletic performance. Rugby and athletic coach, Matt Thomas, told us he never recommends a bulk or cut to his players because “across the board this has been seen to have detrimental effects on athletic output. When a large amount of body weight is cut through drastic intervention, the effects on performance are very clear. Aerobic endurance, maximal oxygen uptake and muscular strength generally fall after rapid body weight reduction, but can be increased with gradual weight loss.”
Can you gain muscle without gaining fat?
Personal trainers have different opinions on the best way to build muscle and look lean. Many professionals and average gym go-ers look to build muscle without the fat gain that a bulking cycle brings.
"The constant cycle of bulking and cutting might be a good way to max out your genetic potential for muscle gain or get shredded for a photoshoot, but that's the territory of body builders," says Scott Laidler. "For a lot of people who are looking to build muscle, a 'lean bulk' or even ‘recomposition’ training phase is the order of the day. This means gaining muscle at a slightly slower rate but without the accompanying body fat.
“I would advise three total-body weight workouts each week, with a modest calorie surplus on training days. For the non-training days, if you eat enough calories to break even, or even have a slight deficit, you can avoid piling on body fat. But what you eat really matters. You also need to be eating quality, healthy fats and carbohydrate to help you perform in your workouts as well as recover.
“Using this method, you'll gradually improve your composition and eventually be in great shape pretty much year-round, which if you aren't on a competition schedule is a much more comfortable place to be,” concludes Scott. Slow and steady really does win the race.
How much should you eat?
You can work out roughly how many calories you need to eat to maintain your weight using our calculator below and adjust accordingly to your exercise schedule. Experts recommend keeping a food diary for a couple of weeks to work out how much you already eat, as it is common to underestimate your calorie intake. From there, you should start out eating at your maintenance calories and increase them very slowly until you begin to see around a one-percent increase in body weight per month with the right amount of weight training. Any more than this and you could risk gaining too much fat.