Contrary to current dietary recommendations, slow and steady weight loss does not reduce the amount or rate of weight regain compared with losing weight quickly, according to new research.
The Australian study was based 200 obese adults who were randomly assigned to either a 12-week rapid weight loss programme on a very-low-calorie diet or a 36-week gradual weight-loss programme. The results of the trial, published today in The Lancet Diabetes & Endocrinology, found that participants in the rapid weight loss group were more likely to achieve target weight loss (losing more than 12.5% of their body weight) than those the gradual weight loss group. Over a three year follow-up period, both groups displayed similar levels of weight regain.
The authors suggest a number of possible explanations for their findings. The limited carbohydrate intake of a very-low-calorie diets may have induced metabolic changes that aided weight loss. Alternatively rapid initial weight loss may also motivate participants to persist with their diet and achieve better results.
Our colleagues at the UK SMC collected the following expert commentary. Feel free to use these quotes in your reporting. If you would like to contact a New Zealand expert, please contact the SMC (04 499 5476; email@example.com).
Prof Nick Finer, Consultant Endocrinologist and Bariatric Physician, University College London Hospitals, said:
“This study has approached the question of rapid versus slow weight loss with a brilliantly clever design. It shows clearly that rapid weight loss does not lead to faster weight regain, but importantly can be a better approach since more people achieved their target loss, and fewer dropped out of treatment. If we couple these findings to those from other groups that have shown dramatic and immediate improvements in diabetes and blood pressure with rapid weight loss, the use of low energy meal replacements should be part of NHS approaches to treatment. Some years ago Counterweight showed this approach could be delivered successfully in primary care.”
“The study does also highlight that while weight loss is hard, weight loss maintenance is even harder. The findings that hormone levels driving hunger were high in those who lost weight, does suggest a role for drugs that reduce hunger to be combined with such approaches to enhance weight loss maintenance rather than used to produce the weight loss in the first instance.”
Prof Nick Finer was an author on some Counterweight papers.
Gaynor Bussell, Dietitian and Public Health Nutritionist, said:
“Rapid weight loss can boost motivation as the rewards appear quite quickly and these formula type diets can also be easy to follow as there is no ambiguity about what to eat. On such a rapid weight loss diet then hunger will be suppressed due to ketone production but ketones can make the blood pH too acidic, which can cause kidney damage at high levels.”
“Most studies have shown slow weight loss to be better for a number of reasons; one of these is that rapid weight loss can mean that more muscle mass is lost than if the weight loss is gradual; thus lowering the rate at which it burns calories. The sample size of this study was probably not enough to look at significance in maintenance of muscle mass.
“Very low calorie diet also are also short of nutrients (around 1200 kcals are needed per day to ensure there is sufficient nutrient intake). So vitamin and mineral supplementation is needed on such diets, which is never as good as getting the nutrients from food. Meal replacement diets can also be expensive, so no an option for everyone who wants to lose weight, and there is no option of re-educating people about better ways to eat
“Both groups gained weight to the same extent when the active weight loss part of the programme was over. What this seems to suggest is that the rapid weight loss was no better than the more gradual weight loss, i.e. both were equally poor in the maintenance arm of the trial. Many diets do not emphasise the aspect of being able to maintain weight, and this is critical. As the paper points out, there are hormone drivers that lead to weight gain and more research is needed in this area.
“We now know that there are several ways of losing weight, some are more healthy than others, but it is important to be able to stick to the diet. There may well be a role for using rapid weight loss diets in some circumstances for some people, but it is important to consider how weight loss will be maintained after the diet is over.
Prof Tom Sanders, Professor emeritus of Nutrition and Dietetics, King’s College London, said:
“This study set out to test whether very low calorie meal replacement, which was expected to result in more rapid weight loss than a conventional weight loss diet, resulted in increased weight gain following the weight loss period. The meal replacement achieved the targeted weight loss in 12 weeks but it took 36 weeks to achieve the target weight loss in the control group. However, after 144 weeks follow-up about 71% of the participants in both groups had regained the weight they had lost.
“The major problem with this study is the difference in the proportions of dropouts on the conventional diet 51% vs. 22% on the meal replacement, which was provided free of charge. The meal replacement diet was also more likely to result in ketosis. What the study does not show is whether the rapid weight loss had a more detrimental effect on muscle mass. Although, not quite significant (P=0.07) the increase in leptin concentration, which reflects the amount of fat in the body, was slightly greater in the meal replacement group but data were only available on 55 and 34 participants so an effect may have been missed because the study was underpowered.
“The authors argue that meal replacements may be more cost effective than conventional dietary advice given by a dietitian (Australian $540 vs $1620). However, the cost of conventional weight loss through groups like Weight Watcher and Slimming World in the UK is much lower (typically £5/week, it would cost £180). It could also be argued that conventional diet advice sustained a lower weight for a longer period of time (180 weeks) than those allocated to the meal replacement treatment (156 weeks). The challenge is not losing weight but sustaining weight loss.”
Prof Naveed Sattar, Professor of Metabolic Medicine at the University of Glasgow, said:
“This appears a well done study but the extent to which it really represents ‘gradual’ weight loss in the control arm of the study is unclear, since losing around 15% weight loss by 8 months would still be considered a rapid weight loss in some minds. For me, gradual weight loss would be a loss of around 3% weight loss at 3 months before a period of weight maintenance- and then individuals can revert to weight loss if so desired. It may be best for the majority of individuals to lose weight even more slowly than in this study and more work is needed in this space to test this.
“Rapid or semi-rapid weight loss in the study appeared to be associated with sustained hunger signals, again arguing for even slower weight loss changes to minimise these hunger pangs.
“This is not really a surprising result, since I would suggest that both conditions represent more rapid weight loss than desirable. We know the body has clever weight loss maintenance and appetite systems to challenge weight change and these will act to revert fast weight changes- thus it may be best to lose weight more slowly than used in this study. One must remember that weight gain in many who are obese has occurred over years and reversal may need to be relatively slow so that the body’s brain and gut homeostatic systems that regulate appetite have time to reset- the present study suggests that too rapid a change in weight lead many to fail with weight loss in the longer term.
“What we need is further studies to identify individuals who may be more successful with rapid weight loss vs. moderate weight loss vs. slow weight loss. Clearly, different people react in different ways to different regimens and we have little knowledge in deciding who may succeed best with what strategy. In the meantime, the use of commercial companies to help most achieve lower weight loss levels in a more sustainable manner remains the best choice.”
Prof Susan Jebb, Professor of Diet and Population Health, University of Oxford, said:
“This is an important and well conducted study. It shows clearly that the common claim that more rapid initial weight loss is associated with more rapid regain is false. This is important because it will enable professionals to recommend a broader range of treatment options so that people may be more likely to find the one that is best suited to their lifestyle. Interestingly, the rapid weight loss group were more likely to achieve their target weight loss and more likely to stick with the programme. These factors are both important to successful weight control.
“Obesity is a chronic, relapsing condition and both groups regained weight. The paper sheds light on some of the hormonal changes which make it harder to maintain a reduced body weight than to avoid initial weight gain and emphasises the need to develop more effective interventions for weight loss maintenance. But, it is also important not to exaggerate the weight regain; after 2 years the mean weight in both groups was still 5% lower than baseline. For the individuals concerned, a weight reduction of this magnitude, approximately one BMI unit, would reduce their risk of mortality by more than 6%. Similarly to other trials with prolonged follow up, the rate of weight regain slows over time, suggesting that the participants will experience a number of years with a body weight lower than baseline which will help to sustain at least part of the health improvements achieved with weight loss.
“The authors suggest that weight loss using a liquid formula diet may be easier to deliver effectively in primary care than traditional interventions that require complex dietary information to be communicated to patients. Trials in routine primary care, outside specialist obesity centres or research units, are urgently needed to consider both the acceptability and effectiveness of more rapid weight loss interventions in this context.
Prof Susan Jebb is Independent Chair of the Public health Responsibility Deal Food Network.