How to Lean Bulk, Cut, and Switch Between the Two Phases

A lean bulk is a 10 to 20 percent calorie surplus, gaining 0.25 to 0.5 percent of bodyweight a week, run for 16 to 24 weeks. A cut is a deficit that drops 0.5 to 1 percent of bodyweight a week, run for 8 to 12 weeks. You switch between them on three numbers: weekly average bodyweight, waist, and your top sets on three lifts.

Most people who bulk and cut for years without changing much do not have the wrong idea. They have no stopping rule. They bulk until a photo scares them, cut until a party, and repeat. This is how to run each phase on numbers, and how to know the exact week to switch.

What each phase is for

A bulk exists to add muscle and strength. The surplus is there to support training and recovery, not to be the point. A cut exists to get lean while keeping the muscle you built. The deficit is there to lose fat, and everything about the way you run it is about protecting the lifts.

If you keep those two sentences in mind, most of the decisions below make themselves. A bulk that is adding fat faster than strength has stopped doing its job. A cut that is costing strength faster than it is costing fat has stopped doing its job. Both are signals to switch.

The bulk numbers

Iraki and colleagues (2019) reviewed off-season nutrition for natural bodybuilders and landed on these targets:

• Surplus of about 10 to 20 percent over maintenance.
• Gain about 0.25 to 0.5 percent of bodyweight a week, with advanced lifters at the low end.
• Protein 1.6 to 2.2 grams per kilogram, fat 0.5 to 1.5 grams per kilogram, carbs at least 3 to 5 grams per kilogram.

For an 80 kg lifter with a maintenance of 2,800, that is 3,100 to 3,350 calories, gaining 200 to 400 grams a week. The full reasoning, including why a bigger surplus buys fat and not muscle, is in lean bulk calories explained.

The cut numbers

Three sources agree on the rate. Helms and colleagues (2014) recommend 0.5 to 1 percent of bodyweight a week for natural bodybuilders getting stage lean. Ruiz-Castellano and colleagues (2021) give the same range for resistance-trained athletes, with protein at 2.2 to 3.0 grams per kilogram. Garthe and colleagues (2011) tested it directly: athletes losing 0.7 percent a week gained 2.1 percent lean mass and got stronger, while athletes losing 1.4 percent a week lost the same fat but added no lean mass.

For the same 80 kg lifter, that is 400 to 800 grams a week, which is a deficit of 450 to 900 calories. Most people should start near the bottom. How big should your calorie deficit be if you lift goes through picking the number.

The three numbers that tell you when to switch

Track these through both phases. Nothing else is needed.

Weekly average bodyweight. Weigh every morning, average the seven days. This is the rate check: are you gaining or losing at the target pace.

Waist at the navel. Once a week, same morning conditions, tape snug but not tight. This tells you what the weight is made of. On a bulk the waist should crawl, half a centimetre a month or so. On a cut it should fall steadily even in weeks where the scale sulks.

Top set on three lifts. Pick a squat or leg press, a press, and a row or pull. Log the best set each week. On a bulk these should climb every two to three weeks. On a cut they should hold within about 5 percent.

End a bulk when

• The waist is up about 5 centimetres from where the bulk started, or
• The scale is rising but the three lifts have not moved in four weeks, or
• You are 20 to 24 weeks in and progress has flattened.

End a cut when

• You reach the waist or bodyweight target you set at the start, or
• Top sets are down 5 to 10 percent for two weeks in a row, or
• You are 12 weeks in and the next step would need a deficit you cannot hold.

None of these are "one bad week". They are two to four weeks of data pointing the same way.

How long each phase should last

Bulks are slow because muscle is slow. At 0.25 to 0.5 percent a week, 20 weeks adds 4 to 8 kg of bodyweight, of which a lean bulk done well might be half muscle. A 10 week bulk adds 2 to 4 kg, and a chunk of that is water and glycogen that vanishes in the first fortnight of the cut. So: 16 weeks minimum, 20 to 24 is better.

Cuts are shorter because the cost rises with time. Eight to twelve weeks at 0.5 to 1 percent a week takes off 4 to 10 kg, which is enough for most people who bulked sensibly. Past 12 weeks, sleep, strength and patience all start to go. If you need longer, split it with a week or two at maintenance in the middle.

Between phases: a bridge. Two weeks at maintenance when moving from a cut into a bulk, adding 100 to 150 calories a week until you reach the surplus. Moving from a bulk into a cut, drop straight to the deficit. The water and glycogen you lose in week one are not muscle.

A worked example: one year, one lifter

Sam is 80 kg at about 15 percent body fat, has lifted for three years, and has a maintenance of 2,800 calories.

Weeks 1 to 20, lean bulk. Surplus of 12 percent, 3,150 calories. Target gain 250 to 350 grams a week. He ends at 86 kg. Waist went from 84 to 88.5 centimetres. His squat top set went from 130 for five to 145 for five. He stops at week 20 because the waist rule (about 5 centimetres) is close and the lifts have slowed.

Weeks 21 to 30, cut. Straight to a 550 calorie deficit at 0.65 percent a week. Protein 2.4 grams per kilogram. He loses 5.5 kg over ten weeks, ending at 80.5 kg with a waist of 83 centimetres, one centimetre under where he started the year. His squat holds at 145 for four. He stops because he hit the waist target.

Weeks 31 to 32, bridge. Two weeks at maintenance, now about 2,850 given the new bodyweight, then add 150 a week up to the next surplus.

Weeks 33 onward, bulk again. Starting from the same bodyweight as January, one centimetre leaner at the waist, with a squat 15 kg heavier. That is roughly 1.5 to 2 kg of muscle in a year, which is about what a third-year lifter can expect. Nothing about the plan was exciting. All of it was measured.

Common mistakes

Switching every four to six weeks. Neither phase gets long enough to do anything. A bulk needs 16 weeks to add real tissue. A cut needs 8 to show it.

Bulking until you are 25 percent body fat. The cut after takes five months and you lose most of the strength you gained. Stop at the waist rule.

Cutting to abs every summer. Six months a year in a deficit is six months a year of not building. If you cut every year, make it short and make the bulk long.

Skipping the bridge. Two weeks of maintenance after a cut lets the scale settle and stops the rebound where you gain three kilos in a fortnight and call it a bulk.

Switching on feelings. One bad photo, one soft week, one comment. The three numbers are there so you do not have to trust how you feel on a Tuesday.

Running a bulk on an untested maintenance. If maintenance was 300 too high, your "small surplus" is a large one. Test it first, using how to find your real maintenance calories.

How to track this in Ultra+

The switch rules above depend on knowing your best set on three lifts every week, and Ultra+ puts that in front of you. Every set you log shows your previous set and your best set, so a new best, or a top set that has slipped 5 percent, is visible the moment it happens. After each session the volume delta shows whether this week beat your last run of the same workout, which is the plain answer to "is the bulk still working".

The nutrition journal handles the other two numbers. It logs bodyweight for the weekly average, and food search with barcode scan makes the surplus or deficit easy to hit day after day, with protein, carbs and fat shown against your target. The weekly card then reviews the week you actually trained, so a soft week in a bulk gets noticed in seven days rather than seven weeks.

Start here

Test maintenance, pick the phase that fits where you are, set the three numbers, and write down the switch rules before day one. The calorie calculator gives you the starting estimate for either phase.