3 fitness mistakes women make trying to lose weight and get lean

By Dan Remon · Evidence checked October 2026

You train 4 or 5 times a week and you eat carefully. Months later the scale has barely moved, and you don’t feel any stronger than when you started.

You’ve already proved you’ll turn up, so discipline isn’t the gap. The gap is where the effort goes.

I started Fitcorp as personal training studios in 2002. Women who work hard and still don’t see a change tend to make the same 3 mistakes, and each one has a fix the research supports.

The 3 fitness mistakes that stop women getting lean

The 3 mistakes I see most are random classes instead of a progressive strength program, not eating enough (protein in particular), and too much cardio with strength squeezed out. All 3 burn calories without building anything that lasts. The fixes are a written strength program 2 to 3 times a week with loads that go up, enough food and protein to protect muscle while you’re in a calorie deficit, and cardio or classes fitted around the strength days. Change one thing at a time, and judge progress on strength and waist measurement as well as the scale.

Mistake 1: random classes instead of a strength program

Class passes and a new studio on every corner make variety easy. If your goal is to stay active and enjoy it, keep going. If you want a specific result, such as less body fat, more strength or a leaner shape, random classes give you random results.

Your body adapts to a demand it meets repeatedly and that grows over time: the same core movements, made gradually harder through load, reps, sets, tempo or rest. That’s progressive overload, and a different class every day never repeats the demand long enough for it to work. I’ve set out the difference in training versus workouts.

Women respond well to it. A meta-analysis of 24 resistance training studies in women, lasting 4 weeks to 12 months, found large improvements in upper body strength and clear gains in lower body strength and muscle size.¹ Training frequency and volume influenced the strength gains, and supervised training had a larger effect on lower body strength than training without supervision.

The other half of this mistake is load. Most people pick weights that are too light when they train alone, and the research on that is in 10 reasons you need a personal trainer. A weight you could lift 20 times does little in a set of 10. Muscle builds over months, it’s what gives you the lean, athletic shape most people are after, and you decide how far to take it.

Instead, do this

• Run a written strength program 2 to 3 times a week, built on a squat, a hinge such as a deadlift, a push, a pull and a carry.
• Repeat the same program for 4 to 6 weeks so the demand can build.
• Choose a weight that leaves 1 to 2 good reps in reserve at the end of each set.
• Log every set. When you reach the top of your rep range, add load next session.

Mistake 2: not eating enough, especially protein

Most downloadable diet plans cut calories with no thought for your training or your schedule, so you end up hungry, flat and training badly. You need a calorie deficit to lose fat. You don’t need to starve the training that shapes the result.

I’ve always explained it with a fire. Feed it a few twigs and it burns out fast. Give it the right fuel at the right time and it keeps burning. Under-eating while you train hard is the twigs.

The research backs a moderate deficit. A meta-analysis of randomised trials of resistance training in an energy deficit found strength gains held up, but gains in lean mass were impaired, and a deficit of about 500 kcal a day was enough to stop them.² The authors’ advice for people lifting to keep muscle while losing weight: avoid deficits larger than 500 kcal a day.

Protein matters most. A meta-analysis of 18 randomised trials compared protein intakes above the Recommended Dietary Allowance (RDA) of 0.8 g per kg of body weight a day with intakes at the RDA. During calorie restriction, the higher intakes reduced the loss of lean mass by about 0.36 kg on average.³ Without a deficit or resistance training, the extra protein made no difference.

For a working target, a meta-analysis of 49 randomised trials in people doing resistance training found gains in lean mass levelled off at a total protein intake of about 1.6 g per kg a day.⁴ Those trials weren’t diets, so treat it as a practical target. For a woman who weighs 60 kg, that’s about 96 g a day. I set it up as 3 to 4 meals with 25 to 30 g of protein each: eggs, Greek yoghurt, fish, chicken, tofu, tempeh or lentils.

Instead, do this

• Aim for a moderate deficit you can hold for months.
• Build each meal around a protein source first, then vegetables, then carbohydrates and fats to suit your training days.
• Track protein and the type of food you eat for 2 weeks before you count every calorie.

If the scale stalls after weeks of eating less, read why the scale stalls, and for a plan built on your own data, see personalised nutrition. If you have a kidney or other medical condition, check your protein target with your doctor first.

Mistake 3: too much cardio, not enough strength

A week of spin, bootcamp and HIIT classes feels productive, but most of it is moderate-intensity volume. Real high-intensity interval training means short efforts at around 8 out of 10 or harder, with rest between them, and nobody holds that for a 45 to 60 minute class. I compare the two in HIIT vs cardio.

Cardio works for fat loss. In an 8-month randomised trial of 119 sedentary adults with overweight or obesity, aerobic training reduced fat mass more than resistance training. The groups that included resistance training gained more lean mass, and doing both took twice the time without cutting significantly more fat than aerobic training alone.⁵

Strength training reduces body fat too. A meta-analysis of 54 randomised trials in healthy adults found that full-body resistance training, compared with no exercise, reduced body fat percentage by 1.46 percentage points, fat mass by 0.55 kg and visceral fat. Sex didn’t change the effect.⁶

So the aim is both, in the right order. Cardio burns fat and keeps your heart and lungs fit. Strength builds the lean mass cardio alone doesn’t. If the class with your friends is the best hour of your week, keep it and fit it around your strength days.

Instead, do this

• Book 2 to 3 strength sessions into your calendar first, on alternate days.
• Fit classes, HIIT, yoga, Pilates or cycling around them on the other days.
• Keep true HIIT short: a handful of hard intervals, once or twice a week.

Fix one mistake per cycle: the Monthly Lever

The temptation is to fix all 3 on Monday. If you run a team, a practice or a business, 3 new habits at once is a second job, and it rarely survives a busy month.

So I install one change per 28-day cycle, the Monthly Lever. One change, held for 28 days until it runs without a second thought, then the next one stacks on top. For these 3 mistakes, the order looks like this:

1. Cycle 1: strength. 2 sessions a week from a written program, every set logged. Classes stay as they are.
2. Cycle 2: protein. A protein source at every meal, adding up to your daily target.
3. Cycle 3: rebalance. Strength days go in the calendar first, cardio fits around them, and a third strength session goes in if the week allows.

Strength goes first because it shapes the result and gives you a log to measure against. The Monthly Lever is part of the Stealth OS, the system I install with private clients and inside The Quest.

Measure more than the scale

When you lose fat and build muscle at the same time, the scale can understate the change. At the end of each cycle, check:

• The loads on your main lifts, from your training log.
• Your waist measurement, taken the same way each time.
• How your clothes fit.
• Your energy and sleep across the month.

A cycle where the scale barely moved but your loads went up and your waist came in has worked. One where nothing moved tells you which lever to pull next. Feedback, not failure.

How to start

1. The 1% Scorecard. 8 questions, 2 minutes, free. You get your Compound Index, the system that’s leaking most and the one thing to install first.
2. Coached training in Bangkok. My team at Aspire Coaching & Physio runs supervised, progressive training, with physiotherapy in the same team.

Pick one mistake, fix it for 28 days, then move to the next.

Related reading: How Colin lost 45 kilograms, How busy exec Niels got lean, fit and focused and How to warm up with purpose: the corrective warm-up I use.

FAQ

Sources

1. Hagstrom, A. D., Marshall, P. W., Halaki, M., & Hackett, D. A. (2020). The effect of resistance training in women on dynamic strength and muscular hypertrophy: A systematic review with meta-analysis. Sports Medicine, 50(6), 1075-1093. doi.org/10.1007/s40279-019-01247-x
2. Murphy, C., & Koehler, K. (2022). Energy deficiency impairs resistance training gains in lean mass but not strength: A meta-analysis and meta-regression. Scandinavian Journal of Medicine and Science in Sports, 32(1), 125-137. doi.org/10.1111/sms.14075
3. Hudson, J. L., Wang, Y., Bergia, R. E., III, & Campbell, W. W. (2020). Protein intake greater than the RDA differentially influences whole-body lean mass responses to purposeful catabolic and anabolic stressors: A systematic review and meta-analysis. Advances in Nutrition, 11(3), 548-558. doi.org/10.1093/advances/nmz106
4. Morton, R. W., Murphy, K. T., McKellar, S. R., Schoenfeld, B. J., Henselmans, M., Helms, E., Aragon, A. A., Devries, M. C., Banfield, L., Krieger, J. W., & Phillips, S. M. (2018). A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. British Journal of Sports Medicine, 52(6), 376-384. doi.org/10.1136/bjsports-2017-097608
5. Willis, L. H., Slentz, C. A., Bateman, L. A., Shields, A. T., Piner, L. W., Bales, C. W., Houmard, J. A., & Kraus, W. E. (2012). Effects of aerobic and/or resistance training on body mass and fat mass in overweight or obese adults. Journal of Applied Physiology, 113(12), 1831-1837. doi.org/10.1152/japplphysiol.01370.2011
6. Wewege, M. A., Desai, I., Honey, C., Coorie, B., Jones, M. D., Clifford, B. K., Leake, H. B., & Hagstrom, A. D. (2022). The effect of resistance training in healthy adults on body fat percentage, fat mass and visceral fat: A systematic review and meta-analysis. Sports Medicine, 52(2), 287-300. doi.org/10.1007/s40279-021-01562-2

This article is general information, not medical advice.