Whether trying to lose pounds or stay the same, it can be frustrating for a person when their weight seems to fluctuate despite their best efforts to control it through diet and exercise.

There are a number of factors which might cause someone to experience weight cycling, or the ‘yo-yo effect’; some of which are more under a person’s control than others.

What is ‘weight cycling’?

Perhaps the simplest way to describe the yo-yo effect is weight loss which is successful in the immediate or short term but unsuccessful in the long term. The person’s weight may go down due to drastic habitual changes such as extreme dieting, but then rise again when this eating regimen proves unsustainable.

There is no clear definition of weight cycling in terms of scale. It can be used to refer to instances where either a relatively small amount of weight is lost and regained, or a much larger amount.

In one study published in Metabolism Journal, moderate weight cycling is defined as losing between 10 and 20 pounds before regaining it

Why does it happen?

Someone may put on weight shortly after losing it for a number of reasons.

Perhaps one of the most common is ‘yo-yo’ or ‘crash’ dieting.

This might involve skipping meals or fasting for long periods, or severely reducing the calorie content of the meals one does eat. It’s a method which has historically been popular among those looking to get quick results.

However, it’s also one which trains the body to metabolise food differently.

Calories are a vital part of the metabolic process. The body converts them into energy, which in turn enables the muscles and organs to function normally.

Obviously people process fat at different rates (several factors play a role in this), but when there is a considerable drop in the amount of calories a person eats, the body’s metabolism will often adapt by slowing down, in an attempt to conserve the energy it has access to.

If someone subsequently ups their calorie intake after adopting an extremely low calorie diet, their body may not adapt to the change in habits quickly, and continue to metabolise calories at a slower rate. Consequently, this fat will be stored by the body in reserve, leading to an increase in weight.

What are the effects of it?

There are several ways in which weight cycling can adversely affect someone.

Psychologically, quickly regaining weight after having lost it can lead to a loss of self-esteem, and can also reduce the motivation to embark on a weight loss programme in future.

Dropping and gaining weight in quick succession can also have short-term physical effects too, causing feelings of lethargy and mood swings.

Can it pose a health risk?

The long-lasting physical effects of weight cycling are a subject of intense debate.

One study which measured the hormone levels of overweight participants after undertaking a 500-550 calorie-per-day diet found that the presence of a variety of hormones responsible for managing appetite was significantly different even one year following completion of the short programme.

The study, albeit one which received significant media coverage, was however deemed to have a number of limiting factors in a report compiled by Baizan and published by NHS Choices.

Conversely, another survey (mentioned above, appearing in Metabolism Journal) found that yo-yo dieting has no long-term detrimental effects on future weight loss attempts or on health; but once again, there were limitations to the study identified by the NHS, including that the findings were based on self-reported data from respondents.

Ultimately, more research is needed in order to determine whether or not weight cycling poses any long-term physical health risk.

Those who are overweight and trying to lose pounds are encouraged to do so at a modest but consistent rate, in order to avoid any health risks which could be related to weight cycling, and to help them maintain a positive mental approach to losing weight.

How do you keep weight off?

A doctor can help someone who is overweight develop and adhere to a plan of controlled and lasting weight loss. This will typically involve a balanced diet, a plan of regular exercise, and if someone’s weight is detrimental to their overall health and these measures alone have not worked, a programme of weight loss medication.