"Possibly the fastest way to instantly look 10 pounds thinner is to assume better posture. Having better posture straightens up the body, putting the spinal column in alignment and bringing the chest forward, thus decreasing the amount of 'abdominal bulge' that you typically would experience while in a more slouched position.
Luckily, getting better posture is very easy if you follow these steps. Being sure to do them on a regular basis will get you very close to always maintaining good posture and help you look your very best.
Tighten The Glutes
The first thing to do to achieve better posture is to think of squeezing the glute muscles. This will cause the hips to shift backward, tightening up the stomach region and making you look slimmer.
In addition this, you'll also get the benefits of a better spinal column position, which will decrease your risk of experiencing lower back pain. Often one of the biggest reasons why people experience low back pain is due to a 'sway back' position, so bringing the hips up will really help with this.
Squeeze The Shoulder Blades
Next, you want to think of squeezing the shoulder blades back and together. This helps to open up the chest and straighten the upper back. When you do this, you automatically improve the amount of confidence you project outwards as well, which makes you again look much better to others.
Raise The Chin
Step three on this better posture plan is to raise the chin ever so slightly. Having a downward tilt with your head is going to make you come across as less confident as well and could cause you to lean forwards slightly, impacting the posture you're holding. While you obviously don't want to be staring at the sky, simply carrying the head high will accomplish exactly what you're looking for.
Set A Timer
Finally, the last thing you want to do is set a timer. Doing so will act as a check on your posture and remind you to straighten up regardless of what you're doing. Even assuming better posture while seated at work will eventually help the posture become habit and that's exactly what you're going for.
As time passes, pretty soon your poor posture habits will be transformed and you won't even need to think about better posture any more. Give it about two to three weeks for better habits to be fully formed as this is typically how long it takes to change old bad habits. Also, the more frequently you are checking your posture throughout the day, likely the sooner the good habits will be formmed." (Continued via Ezine Articlee, Ernest Anfuso) [Ergonomics Resources]