The secret to beating the battle of the bulge is a steady - rather than dramatic - reduction in calories, say scientists.
A study of almost 200 people found those whose weight fluctuated most during the first few weeks of a diet were less successful one and two years later.
The men and women who lost a consistent number of pounds each week fared best - despite it being just a little.
For example a participant who lost four pounds one week, regained two and then lost one the next, tended to end up worse off than one who lost a pound each week for three weeks.
Psychologist Professor Michael Lowe, of Drexel University, Philadelphia, said the findings illuminates a potential method for sticking to goals.
This would be based on a mathematical formula, or algorithm, that would calculate
weekly, or even daily, weight variability.
He said: “Settle on a weight loss plan that you can maintain week in and week out, even if that means consistently losing three quarters of a pound each week.”
The research could lead to improvements in personalised diets based on a mathematical formula, or algorithm, that would calculate weekly, or even daily, weight variability.
Most people maintain their weight inconsistently and fall into the vicious cycle of losing and then gaining weight.
More than six in ten British adults are overweight, with a shocking quarter obese.
Experts predict by 2025 four in ten will be obese with Type 2 diabetes continuing to soar.
Research has revealed two thirds of all dieters pile their weight back on within three years of hitting their dream targets.
In fact 40 per cent of those who lose more than 7st put on at least that much again.
It is called the Fat Trap.
Women put themselves on an average of 16 diets during their lifetimes, fuelling a £2 billion diet industry in the UK alone.
Slow and steady
Now principal investigator Prof Lowe and colleagues have shown shedding consistent pounds each week is the key to overcoming the problem.
They said: “When it comes to losing weight, it is not necessarily slow, but steady, that wins the race.”
In the study published in Obesity, they enrolled 183 participants aged 18 to 65 - eight in ten of them women - in a weight loss program and followed them over a two year period.
Lead author Emily Fieg, a PhD graduate student, said: “It seems that developing stable, repeatable behaviours related to food intake and weight loss early on in a weight control program is really important for maintaining changes over the long term.”
The psychologists were interested in studying what makes some people less successful at dieting - and identifying predictors that could improve treatment outcomes in the future.
To find out they recruited overweight or obese volunteers into a year long weight loss program that used meal replacements along with behavioural goals such as self monitoring, calorie counting and increasing physical activity.
The participants attended weekly treatment groups during which they were weighed, and returned for a final weigh in two years from the start of the program.
The participants also reported on food-related behaviours and attitudes like cravings, emotional eating, binge eating and confidence in regulating intake.
The researchers found that higher weight variability over the initial six and 12 weeks of weight loss treatment predicted poorer subsequent, long-term weight control at 12 and 24 months.
Binge eating bad
Interestingly individuals who reported lower emotional eating, binge eating and preoccupation with food at the start showed higher weight variability and less weight loss overall.
The researchers said: “This suggests initial weight change, rather than relationships with or behaviours toward food, is much more important in predicting who will succeed in weight loss and maintenance.”
Exactly why some people have more weight variability than others is a question the researchers are interested in exploring in future studies.
If these can replicate the results then measuring weight variability may be a way to identify individuals who are less likely to achieve meaningful and sustainable weight loss, and who may benefit from a stronger, more tailored focus on consistency.
Prof Lowe said: “Higher variability in weekly weights during the first 6 and 12 weeks
of treatment predicted poorer subsequent weight loss 1 and 2 years
after treatment initiation.
“If found to be reliable and useful, weight variability early in treatment may be cause for supplemental intervention.
“An algorithm could be created to calculate weight variability after each week - or even after each day, given the development of new technologies to monitor weight at home - of a weight loss program to be used by program leaders as a clinical indicator for risk of poor outcomes.
“Future research should also examine the behavioral and/or metabolic basis for weight variability and whether increasing the stability of week-to-week weight losses improves long term outcomes.
“If this is the case, behavioural interventions may benefit from a stronger focus on consistent weekly weight losses.”