“Eat 500 fewer calories than you burn” is the most repeated line in fitness, and it is also the least complete. A 500-calorie gap means something entirely different to someone with 60 pounds to lose than to someone trying to drop from 15 percent body fat to 10.
Start with the rate
The deficit should follow the pace at which you can lose fat while keeping muscle. A useful rule of thumb is 0.5 to 1 percent of body weight per week for most people. Leaner dieters should go slower, because the body defends the last fat stores harder and aggressive cuts cost disproportionate muscle. People with more to lose can move faster early, then ease off as they lean out.
One pound of fat stores roughly 3,500 calories, but take that as a rough anchor, not a law. Hall and colleagues (2011) modelled human energy balance and showed weight change responds to a deficit in a curved, not straight, line, because metabolism and water shift as you shrink. The old “3500 equals a pound” arithmetic overshoots what actually happens week to week.
Three ways to set the deficit
Percentage of TDEE, the one I would pick. Take 15 to 25 percent off your total. This scales by itself: a bigger person gets a bigger absolute cut, which is what you want. If the TDEE calculator estimate is 2,600, a 20 percent deficit lands near 2,080.
Fixed subtraction. Cutting 300 to 500 calories is simple and fine for average builds, but clumsy at the extremes, too steep for a small person and too timid for a large one.
Goal-weight method. Eat what would maintain you at your target weight. Elegant in theory, easy to undershoot in practice if the goal is far away.
Protein is the lever that spares muscle
In a deficit, protein matters more than it does at maintenance. Morton and colleagues (2018) pooled 49 studies and found that intakes around 1.6 grams per kilogram per day were enough to maximise muscle retention during resistance training, with little extra benefit above that. Pasiakos and colleagues (2013) found higher protein helped preserve fat-free mass during energy deficit specifically. That is why the commonly used range of 1.6 to 2.2 grams per kilogram for active people is not vanity, it is damage control.
Fat should not crater either; around 0.6 to 0.8 grams per kilogram is a reasonable floor, since very low fat intake disturbs hormones and makes meals miserable. What remains goes to carbohydrates, which should mostly fuel your training. Our macronutrient calculator splits the target by goal so you are not doing the arithmetic by hand.
Keep the load on the bar
The signal that tells your body to hold muscle is mechanical tension. Resistance training through a deficit is the difference between losing fat and merely getting smaller. Keep the weight heavy even as volume drops, because if you stop challenging the muscle, the body has no reason to keep an expensive tissue it is not using.
Cardio earns its place as a way to raise expenditure without cutting food further, not as punishment for eating. Extra steps are the underrated tool here, because added NEAT does not make you hungry the way hard cardio often does.
Reading a real plateau
Scale weight stalls for reasons that have nothing to do with fat, so judge progress over two-week blocks using a weekly average of daily weigh-ins. If the average has not moved in 14 days, check intake drift first, then NEAT drop, and only then trim 100 to 150 calories or add 1,500 to 2,500 steps. Do not answer a stall by slashing 500 more; that is how people end up at 1,200 calories, stalled and miserable.
When to step off the diet
Planned maintenance breaks are not failure. A week or two at maintenance every 8 to 12 weeks restores training, resets some of the adaptive response, and makes the next block more productive. Fothergill and colleagues (2016) showed how far metabolic rate can stay suppressed after weight loss, which is one reason the return to maintenance is worth planning rather than guessing. Use the maintenance calorie calculator for that number, because after months of restriction most people badly underestimate what maintenance really is.
References
- Hall, K. D., et al. (2011). Quantification of the effect of energy imbalance on bodyweight. The Lancet, 378(9793), 826–837.