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GMS Health Innovation and Technologies

EuroScan international network e. V. (EuroScan)

ISSN 2698-6388

Overweight and obesity: The efficacy of diets for weight maintenance after weight loss

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  • corresponding author Dieter Korczak - GP Forschungsgruppe, Institut für Grundlagen- und Programmforschung, München, Germany
  • Christine Kister - GP Forschungsgruppe, Institut für Grundlagen- und Programmforschung, München, Germany

GMS Health Technol Assess 2013;9:Doc06

doi: 10.3205/hta000112, urn:nbn:de:0183-hta0001122

This is the English version of the article.
The German version can be found at: http://www.egms.de/de/journals/hta/2013-9/hta000112.shtml

Published: June 10, 2013

© 2013 Korczak et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.en). You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.

The complete HTA Report in German language can be found online at: http://portal.dimdi.de/de/hta/hta_berichte/hta345_bericht_de.pdf


Abstract

The report examines which diets are successful as therapy for overweight and obese persons. In general all considered diets are effective. Besides the food the patients have to change the kinesic behaviour and the lifestyle to achieve sustained success.

Keywords: body mass index, diet, meal replacement, obesity, overweight, weight loss


Summary

Health political background

Overweight and obesity are typical phenomena of affluent societies and are one of the most serious public health problems. In 2012 nearly one in two German adults (men: 67.1%; women: 53%) has overweight. Around one in four adults is obese (men: 23.9%; women: 23.3%). Obesity as chronic disease shows a limited quality of life and a high morbidity and mortality risk. A problem which is not yet solved is that dietary and behavioural as well as extensive lifestyle programmes have a long-term effect only for a few affected persons (yo-yo effect).

Scientific background

The International Statistical Classification of Diseases and Related Health Problems, 10th revision (ICD 10) lists “Obesity and other hyperalimentation” as disease in E65 to E68 in chapter IV. The differentiation of obesity with varying degrees of severity is usually based on the body mass index (BMI). Overweight among adults begins with a BMI of 25 kg/m², as of ≥30 kg/m² overweight is defined as obesity. Depending on the degree of obesity there is a risk for secondary diseases: Obesity class I (BMI 30 to 34.9 kg/m²) shows an increased risk, obesity class II (BMI 35 to 39.9 kg/m²) a higher risk, obesity class III (BMI ≥40 kg/m²) a very high risk.

In the scientific literature several factors are discussed as the cause of overweight and obesity: genetic factors, prenatal and early childhood factors, family disposition, lifestyle, permanent stress, psychosocial reward mechanisms, central control mechanisms in the brain and especially the nutrition and activity behaviour as well as obesogenic living conditions.

The primary aim of obesity therapy is not the maximum possible reduction of weight but the long-term maintenance of a moderate reduced weight (5 to 10% of the original weight). This can be achieved by different forms of therapy. The German Obesity Society recommends a step programme. Thus, they recommend to reduce the fat intake during the weight reduction period and to increase the energy consumption of at least 2,500 kcal/week. For the weight maintenance period the Society recommends a moderate reduced mixed diet and an energy consumption by at least 1,500 kcal/week. In the short-term a higher weight loss can be achieved with a meal-replacement with formula-diets or a formula-diet as replacement of the daily ration. The diets should be accompanied by behavioural therapy.

A criterion for a sustainable and long-term successful weight maintenance is when the therapy goal after six to twelve months is achieved and retained.

Medical research question

The health technology assessment (HTA) report examines which diets (low-fat, high-protein, low/high-carbohydrate, low-calorie, vegan, meal-replacement) are effective for a long-term weight maintenance.

Economic research question

The report examines the cost-benefit-ratio of individual obesity therapies for a sustainable weight maintenance.

Ethical research question

The report analyses the ethical-social implications and the social determinants and effects of obesity.

Methods

In April 2012 a systematic electronic database search had been conducted in 32 databases (e. g. Cochrane, MEDLINE, EMBASE, SciSearch), complemented by hand search. English and German publications from 2007 to 2012 were considered. Keywords such as overweight, obesity, diet, sustainable weight reduction were used. The evidence judgement was based on the evidence classification of the Oxford Centre of Evidence-based Medicine.

Medical results

The report comprises 33 medical studies. The studies are mainly from Anglo-American countries, particularly from the USA (14 studies), only one study is from Germany. Almost all studies show a high evidence (evidence level 1A to 2C) due to their study design (meta-analysis, randomised controlled trials [RCT]), only two studies have low evidence (evidence level 4).

The results show a large range of deviation due to their different intervention and follow-up-periods. In several studies the target of the maintenance of a 10% weight loss is reached. In one study low-fat diets can stabilize a 18% weight reduction from the original weight after nine months. However, the drop-out-rate is very high (49%). According to another publication, high-protein diets can maintain a weight reduction of 14,7% after 15 months. Again the drop-out rate is high (41%). In one study the high-protein diet achieves a weight maintenance of 9.7% after twelve months (drop-out rate 36%). Three study results about effectiveness of high-carbohydrate diets are available. One study shows a weight loss of 13% after 15 months, the second study 8% weight loss after twelve months, the third study shows 4% after 30 months. The results about low-carbohydrate diets are ambiguous. One systematic review demonstrates that low-carbohydrate diets can reduce weight more effective for a short term than low-fat diets, but low-fat diets support a loss in weight within three years.

Five studies deal with the effectiveness of reduced energy consumption on a permanent weight maintenance and can verify this, although with varying degrees of success. The calorie-reduction is normally approximately 500 kcal, hence the daily energy intake is approximately 1,500 kcal. About one year after the end of intervention a weight reduction of 7.6 to 9.4% can be maintained with this type of diet. After nearly 30 months the weight reduction is 4%. Only one study deals with the effectiveness of vegan diets. It records a weight loss of 5.6% after one year and 3.5% after two years.

Six studies examine formula-diets as successful weight reduction and maintenance measure. However, the results vary considerably and range from 2.5% weight reduction after 34 weeks to about 10% in the follow-up after twelve months. Patients with obesity class III achieve a weight maintenance of about 23.5% after 30 months when combining meal-replacement with formula-diets and behaviour therapy. Combined programmes consisting of diet and physical activity obtain a bigger long-term weight loss than an intervention which is based only on diet.

A behaviour therapeutic intervention which includes strengthening of self-regulatory action patterns such as regular control of weight, encouraging after successful weight loss and immediate counteracting when weight is gained, achieves a weight maintenance of minus 15% after 18 months compared with the original weight.

On the whole the following factors show effectiveness for weight maintenance: a daily calorie deficit of 400 to 600 kcal, regular physical activity (2,000 kcal/week), low-fat intake, generous consumption of fruits and vegetables, regular use of meal-replacements, self-monitoring and ongoing coaching or behaviour therapy support, especially in terms of a multi-component programme. The support of a group and the regular attendance of group meetings are connected to further significant weight losses in the weight maintenance period. For the success of weight maintenance measures it is essential that nutritional counseling considers the individual needs, abilities and ressources of the patient as well as the specific risk factors and sets realistic goals.

Economic results

The studies provide no answer to the economic question. Only one US-American study states that the costs for medication were reduced from 157 US-Dollar (USD) per week to 57 USD due to the therapy. This study also shows that an obesity therapy can be an effective and more cost-efficient alternative to surgery for patients with obesity class III.

Ethical results

There is only one US-American study which answers the ethical-social question. It stresses the importance and the influence of obesogenic living conditions on the success of weight maintenance measures and for the realisation of social justice.

If the neighbourhood, the working and living environment is dominated by energy-dense, low-cost fast-food restaurants on the one hand and by a scarcity of appealing fresh fruits and vegetables as well as affordable leisure facilities for physical activity on the other hand, the chances for the residents of those communities are poor to live a healthy life.

Discussion

The aim to maintain a 10% weight loss in comparison to the original weight over a long period is challenging. Apart from the type of diet participants achieve this goal only in very few studies. The evaluation of the studies is hampered by the fact that most studies record only the average percentage of weight loss of the whole group. The number of what percentage of participants can actually maintain >10% of their weight loss lacks in most studies. A further essential limitation is that the weight maintenance period is below one year in several studies which makes it difficult to assess the sustainable effect of the diet and the weight management programme. Furthermore, many studies record a high drop-out rate and a high loss to follow-up. This restricts the value of the study results. The evaluation of the actual nutritional status of the participants is difficult in the study set-up. In most cases the participants are self-reporting on the basis of dietary records. This could lead to a bias of the results as only a small number of studies examines the truthfulness of the records by biochemical analyses. Another confounder which is not controlled sufficiently in several studies is the potential influence of physical activity on weight loss. Furthermore, several studies record only a small number of cases, in- and exclusion criteria are not precisely defined and the comparability of the groups or studies is limited. Three studies must be seen critical regarding the financial support. None of the studies was conducted as double-blind and placebo-controlled RCT. The majority of the studies however has at least a randomised controlled set-up, only four studies do not correspond to this standard and are therefore limited in their informational value.

Conclusion

Taking into account the identified effective factors a successful weight maintenance can be achieved with the use of diets (low fat/energy, high-protein/carbohydrate), mainly with multi-component diet. Due to the numerous intervening external factors of an obesogenic living condition weight maintenance after weight loss is difficult, especially for obese persons with socially disadvantaged background. Here is a public health need for action. Preventive measures should affect consequences of urbanisation, the infrastructure and food supply and could touch advertising and marketing measures. Research gaps exist regarding the cost-effectiveness of diets and the question to what extent socially disadvantaged persons can be reached by obesity therapies.


Notes

Competing interests

The authors declare that they have no competing interests.

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