You Can Strengthen Your Abs. You Can’t Tell Your Body Where to Lose Fat.

How many of us have spent weeks doing sit-ups because the problem was belly fat—or added endless squats because we wanted slimmer upper thighs? The logic is almost irresistible: exercise the area, burn the fat sitting on top of it. Unfortunately, one part of that equation listens very well. Your muscles. The fat is considerably less cooperative.

How many sit-ups does it take to get rid of belly fat?

I suspect many of us have tried to find out.

The stomach looks softer than we would like, so we start doing crunches. The upper thighs bother us, so we add squats, lunges and whatever exercise promises to “melt thigh fat.” Arms? Triceps extensions.

It feels logical.

If a muscle is working hard enough to burn, surely the fat sitting directly above it ought to get the message.

Except that is not how fat loss reliably works.

What 100 Sit-Ups Do

Sit-ups are not useless.

Far from it.

They train muscles in and around your midsection, and repeated abdominal training can improve muscular endurance. What they cannot reliably do is instruct your body to take the energy for those repetitions specifically from the layer of fat covering your stomach.

There is a wonderfully straightforward experiment that illustrates this.

Researchers randomly assigned 24 sedentary adults either to a control group or to six weeks of abdominal training. The exercise group performed seven abdominal exercises, five days a week.

After six weeks, they had not significantly reduced body weight, overall body-fat percentage, abdominal fat, waist circumference or abdominal skinfold measurements.

But they did get substantially better at abdominal exercise.

Their curl-up endurance improved.

That is almost the entire spot-reduction story in one experiment.

The abs received the training.

The abs adapted.

The belly fat did not obediently disappear.

Your Upper Thighs Do Not Take Orders Either

The same problem appears when researchers train only one limb.

In one particularly determined experiment, 11 participants trained one leg for 12 weeks. And this was not a casual set of leg extensions: each training session involved roughly 960 to 1,200 repetitions with the non-dominant leg.

If exercising a particular body part reliably emptied its nearby fat stores, that leg should have had every opportunity.

It didn’t.

The researchers found no significant reduction in fat mass in the trained leg. Total fat mass did fall, but the measurable reductions occurred in the trunk and upper extremities rather than preferentially in the leg doing all that work.

Imagine doing a thousand repetitions for your left thigh only to discover that your arms got leaner.

The human body has a sense of humour.

The Bigger Studies Are Even Less Encouraging

Individual experiments can be small, so the more interesting question is what happens when researchers look across many of them.

A systematic review and meta-analysis published in Human Movement examined 13 controlled studies involving 1,158 people, comparing fat changes in locally trained areas with untrained areas.

Across 37 comparisons, the combined effect was essentially zero.

The researchers found no evidence that repeatedly training one area caused preferential loss of the fat stored there.

So doing more crunches because you want less abdominal fat is a little like repeatedly washing one window because you want the whole house to get cleaner.

You are accomplishing something.

Just not exactly the thing you intended.

But the Science Has One Interesting Wrinkle

I would not go quite as far as saying that every experiment ever performed has found absolutely nothing.

A few small studies have reported evidence of localized fat changes under particular exercise protocols.

For example, a 2017 trial involving just 16 women found greater regional fat loss when resistance work for one part of the body was followed by endurance exercise using another.

And a 2021 study using a specially designed circuit-training programme reported localized reductions around the abdomen. But only 14 participants completed that study—seven in each group—and the spot-reduction group also lost body weight overall.

Those results are interesting.

They are not a good reason to start doing 500 crunches before breakfast.

Taken together, the broader evidence still does not give us a dependable exercise prescription for telling the body, “Take the fat from here, please.”

Then Why Train the Area at All?

Because losing fat is not the only reason to exercise a muscle.

This is the part that gets lost when people say, “Sit-ups don’t work.”

They absolutely work—if what you want is better-trained abdominal muscles.

The six-week abdominal study is a perfect example: the participants did not lose belly fat, but their abdominal endurance improved significantly.

Squats can train your legs.

Rows can train your back.

Resistance exercises can make particular muscles stronger and, depending on the training programme, larger.

What they cannot promise is that the layer of fat sitting immediately above those muscles will be the first place your body decides to shrink.

What I Wish I’d Known Earlier: an exercise is not failing simply because it does not make the fat above that muscle disappear. We were asking the exercise to perform a job it was never particularly good at doing.

If Belly Fat Is the Goal, Think Bigger Than Your Belly

If reducing body fat is appropriate for you, the useful strategy is much less glamorous than a “10-minute belly-fat workout.”

Think whole body rather than body part.

Move regularly.

Do some resistance training.

Include cardiovascular activity you can actually tolerate long enough to keep doing.

And if fat loss is the objective, your eating pattern ultimately has to support the overall energy balance required for that loss.

Exercise can absolutely change body composition. Research examining weight-loss interventions finds that changes in total body fat are associated with reductions in both abdominal subcutaneous fat and visceral fat.

You simply do not get a menu asking which centimetres you would like removed first.

You Can Still Work on the Area You Care About

There is also nothing wrong with wanting stronger abs, firmer legs or more developed shoulders.

Train them.

Just separate the two goals in your mind.

Target the muscle with exercise.

Approach fat loss as a whole-body process.

That distinction saves an astonishing amount of frustration.

Because if you have been doing sit-up number 347 wondering why your stomach has not received the memo, the problem is probably not that you need to reach 500.