Well, it turns out there's a few reasons for this unjust conundrum.
One is that due to the hunger we're exposed to while dieting - which slows down our metabolism - and makes us hungrier.
Speaking to news.com.au, Dr Tim Crowe, a nutrition scientist, said:
The influence of hunger on weight regain is three-times stronger than a slowing of metabolism.
Add the two together it appears almost inevitable that the lost weight will creep back on again for most people.
A recent clinical trial that tested a new diabetes drug which worked by making the kidneys excrete more glucose (a favourable side effect for weight loss) showed that people on the drug only lost slightly more weight than the control group (on a placebo), because the people in the drug treatment group were hungrier.
It drove them to eat an extra 100 calories each day for every kilogram (2.2 lbs) of weight they lost.
In other words, the more weight you lose, the more you eat, and after dieting, we tend to overcompensate for the months of hunger - by eating more.
The best thing to do to avoid this is to avoid quick fix diets that promote 'starving yourself' - instead eat the right things to provide a healthy balanced diet.
Most people see weight-loss as an on or off regime, and binge-watch the second they hit their goals.
Turns out the best thing to do is not cut out foods in the diet you craft in the first place - teach yourself to have a healthier general outlook rather than a quick fix to shred a few pounds.
The good news is - your self control isn't to blame.
Dr. Crowe says that:
Regaining weight has little to do with poor self-control.
Our bodies are primed to fight against weight loss.
You can ignore hunger cues for a time, but they will persist for much longer than your willpower.
Restrictive thinking, in effect cutting out certain foods entirely, is destined for defeat.
The fix for this is to identify your triggers to overeat which might be boredom, stress, fatigue or even skipping meals and build coping mechanisms that aren't based around food - such as exercise, relaxation or socialising.