Unless you're a health and fitness disciple who gets on the weighing scale and stands in front of the mirror with a measuring tape way too often, you probably won't realize when you're packing on the pounds - or if you've lost any.

Once you realize you've reached the point of OMG I'M OVERWEIGHT you might finally be motivated to do something about it.

Unfortunately, when you're at the starting point of I REALLY NEED TO EXERCISE, you might discover the desire to leave it till the next day because Modern Family is on the telly tonight, and the next day because you have to fold your laundry, and the next day because you have to rearrange your iTunes playlist. In the end, you'll only start brisk walking some two months later, before going back to couch-potatoism indefinitely.

And there's a perfectly valid explanation for this all-too-familiar scenario.

This resistance might be all in your head, according to a recent study published in The International Journal of Obesity, which suggests that overweight women's brains are turned off by physical activity. Instead, they're turned on by thoughts of lounging or relaxing. The opposite was found to be true for lean ladies, whose brains were positively stimulated by images of people mid-workout.

The two-part study conducted by scientists of the Key Laboratory of Cognition and Personality at Southwest University in China looked at 13 healthy young women of normal weight, and 13 overweight or obese young women, who were asked if they thought exercise was desirable and if they expected it to be unpleasant.

Participants were then shuffled inside an MRI scanner and shown two sets of pictures:

1. People enjoying exercise.
2. People exhibiting sedentary behaviors.

They were asked to imagine themselves doing these activities from inside the machine, and while doing so, the MRI scanned their brain activity.

The results:

When overweight women were shown images of people working out, the area of the brain that processes urges to like things (called the putamen) demonstrated little activity - suggesting they didn't enjoy what they saw. In addition, the area of the brain that deals with negative emotions lit up at the sight of those images.

Meanwhile, the putamens of the lean women lit up at the thought of exercising, suggesting they look forward to it.

The findings were found to be related to the answers participants had given before the MRI: Overweight women said they expected exercise to end in "embarrassment" from not doing it well or correctly.

How do you get over this hurdle?

Lead study author Todd Jackson suggested that if you're overweight and dread exercise, you could try a reward strategy for working out more. For example, allow yourself to watch your TV series or movies only after you've done 30 minutes of cardio of strength training.

Also, if you're gymtimidated, you can hire a personal trainer, or go for workout videos which you can do in the comfort of your home.

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