It is the question on every dieter's lips... when will people notice the pounds dropping off?
A host of diets promise to help transform the body, while countless studies reinforce the need to combine healthy eating with regular exercise.
But now, a new piece of research has taken the weight-loss conundrum one step further.
And its conclusion is seemingly simple, you need to shed eight to nine pounds, just over half a stone, before your friends and family will notice it in your face.
However, in order to appear more attractive to the opposite sex, it is necessary to double that weight loss, and shed 15 pounds - just over one stone.
Researchers at the University of Toronto revealed in order for anyone to look more attractive, it is important they lose weight from their face.
For even if our waists appear slimmer just losing a few pounds is not enough for others to notice.
It's not until the weight loss affects a person's face that they are likely to be inundated with compliments.
Dr Nicholas Rule of the University of Toronto Department of Psychology said: ‘Women and men of average height need to gain or lose about three and a half and four kilograms, or about eight or nine pounds, respectively, for anyone to see it in their face.
‘But they need to lose about twice as much for anyone to find them more attractive.’
Researchers found that facial adiposity – which is the perception of weight in the face – is an accurate indicator of a person’s body mass index (BMI).
It is also a robust indicator of a person’s health, since higher facial adiposity is associated with a variety of health problems, from a compromised immune system to poor cardiovascular health.
The study sought to determine at what point a change in the perception of facial adiposity occurs.
They created a collection of male and female faces between 20 and 40 years old, in which all of the subjects had neutral expressions, their hair pulled back and no facial adornments.
They also altered each image to create a sequence of photos showing a range of weights on a gradually increasing scale.
Study participants were asked to compare randomly drawn pairs of faces from each sequence and identify the heavier-looking one.
BMI is calculated as a person’s weight in kilograms divided by the square of the person’s height in meters.
Through their trials, researchers determined that a body mass index change of approximately 1.33 kg/m2 is required for a difference in weight to be noticeable.
The study also looked at the threshold at which a person’s facial adiposity led people to find them more attractive.
Researchers concluded that women need to have a BMI of 2.38 kg/m2 to appear more attractive, while men need to lower their body mass index by 2.59 kg/m2.
研究发现，女性的身体质量指数需达到2.38 kg/m2才会看起来更加迷人，而男性则需要将身体质量指数降至2.59 kg/m2。
That translates to approximately 14 and 18 pounds (or 6.3 and 8.2 kilograms) respectively for women and men of average height.
‘The difference between the groups suggest women’s facial attractiveness may be more sensitive to changes in weight,’ Dr Rule said.
‘This just means women attempting to lose weight need to shed slightly fewer pounds than men for people to find them more attractive.’