noncommunicable diseases ( ncds ) are steadily rising , affecting both developing and developed countries .
this is a consequence not only of population aging , but also of the nutrition transition towards westernized diets and sedentary lifestyles .
the nutrition transition is fueled by socioeconomic and technological development as well as globalization and accelerated urbanization . among the nutrition - related ncds
, diabetes is a major concern because its prevalence is rapidly increasing worldwide and particularly so in developing countries .
this number is expected to reach 592 million by 2035 , with the middle east , south east asia , and africa showing the fastest increase in the number of cases . according to the international diabetes federation , 80% of people suffering from diabetes live in low- and middle - income countries .
diabetes is associated with several complications , leading to morbidity , disability , and premature mortality [ 2 , 3 ] .
type 2 diabetes ( t2d ) is by far the most common form of the disease .
diabetes also entails a heavy economic burden for patients , households , and healthcare systems [ 4 , 5 ] .
t2d is a lifestyle disease , which can and should be prevented by intensive lifestyle interventions , characterized by changes in dietary habits and increased physical activity . indeed , lifestyle interventions at the prediabetes stage have proved successful at reducing the incidence of t2d by 28.5% to 58% , in china ( da qing ) , india ( indian diabetes prevention program : idpp-1 ) , finland ( diabetes prevention program , dpp ) , and the united states ( diabetes prevention program and outcomes study , dppos ) [ 68 ] .
weight control is key to the prevention and management of diabetes independent of dietary composition .
as obesity is a major risk factor for t2d , lifestyle interventions aimed at weight loss or control are also critical to prevent t2d . except for india and china , few studies
have been conducted to date on diabetes prevention programs in low- and middle - income countries . in developed nations and
even more so in low - resource countries , healthcare spending is a critical economic and political issue .
a recent world health organization report recommended addressing common lifestyle risk factors for ncds , considering their cost - effectiveness , and their relative ease , and speed of implementation . in resource - limited settings in particular , decision makers require information on the economic burden of ncds , particularly t2d , and of the potential added value of lifestyle interventions for health and development . the economic evaluation of various preventative interventions is important in view of the urgent need for developing countries to set these ncds as a public health priority , of the rapid increase in diabetes prevalence and of substantial variations in lifestyle intervention components and delivery .
there are limited systematic reviews on this topic and the most recent ones covered the period of 19852008 [ 12 , 13 ] .
most economic evaluations of t2d prevention programmes pertained to developed countries partly owing to lack of relevant data in developing countries , while cost - effectiveness tends to be context - specific .
our objective was to review economic evaluation studies of lifestyle interventions for the primary prevention of t2d and also for the control of obesity as key risk factor , based on data published since 2009 .
this review was intended to update knowledge on the cost - effectiveness of t2d prevention .
in order to identify all relevant studies performing an economic evaluation of lifestyle interventions to prevent t2d and for obesity control , we searched the following databases : pubmed , medline , the british national health services economic evaluation ( nhs ees ) , cinhal , econ lit , web of sciences , embase , and latin american and caribbean health sciences literature ( lilacs ) .
we restricted our search to studies published in french , english , or spanish between january 2009 and december 2014 as previous systematic reviews included studies published between 1995 and 2008 .
we used medical subject headings ( mesh ) and other relevant terms to the topic as major constructs to build our search strategy .
the mesh or other relevant terms are related to economic , diabetes , and intervention constructs . to combine these , we used boolean operators  and  and  or  as appropriate .
in addition , the reference lists of all included studies were scanned to identify any additional potentially relevant reports .
for example , the pubmed search combined ( i )  cost - benefit - analysis ( mesh )  or  costs and cost - analysis ( mesh )  or  cost - benefit ( title )  or  cost - effectiveness ( title )  or  cost - utility ( title )  or  economic evaluation ( title )  and ( ii )  type 2 diabetes ( mesh )  or  non insulin dependent diabetes ( mesh )  or  gestational diabetes ( mesh )  or  obesity ( mesh )  or  impaired glucose tolerance ( title )  or  prediabetes ( title )  and ( iii )  diet ( mesh )  or  physical activity ( mesh )  or  diet therapy ( mesh )  or  lifestyle ( mesh )  or  risk reduction behaviour ( mesh )  or  prevention ( title )  or  lifestyle modification ( title )  or  lifestyle advice programme ( title )  or  non pharmacological prevention ( title )  .
appendix shows the majors constructs used in our search strategy . in order to select the relevant studies for this review
, we screened titles and abstracts using a three - stage process . at the first stage , two authors ( koffi alouki and clara bermdez - tamayo ) independently selected studies based on abstracts and titles .
, the same coauthors resolved the disagreements . on the basis of full assessment and discussion of each study
the study selection was guided by the following inclusion criteria : original research articles published in peer - reviewed journals were candidates for inclusion.type of economic evaluation : the selected studies conducted a full economic evaluation as defined by drummond et al . .
 full economic evaluations  are studies in which a comparison of two or more treatments or care alternatives is undertaken and in which both the costs and outcomes of the alternatives are examined in terms of cost - effectiveness , cost - utility , or cost - benefit analyses.the participants : the population groups targeted for the primary prevention of t2d were adult subjects ( over 18 years old ) who were at high risk of developing the disease because of obesity , impaired glucose tolerance , impaired fasting glycaemia , or gestational diabetes.the interventions : we considered dietary modifications or physical activity or both to prevent t2d or control obesity.the comparison : any comparison arm or group used against the lifestyle intervention was accepted for this review.outcomes : these were cost per qaly ( quality adjusted life years ) gained , cost per life year gained , cost per daly ( disability adjusted life years ) averted , cost per diabetes case averted , and other relevant outcomes.studies published between january 2009 and december 2014.studies that were published in english , french , or spanish .
type of economic evaluation : the selected studies conducted a full economic evaluation as defined by drummond et al . .
 full economic evaluations  are studies in which a comparison of two or more treatments or care alternatives is undertaken and in which both the costs and outcomes of the alternatives are examined in terms of cost - effectiveness , cost - utility , or cost - benefit analyses .
the participants : the population groups targeted for the primary prevention of t2d were adult subjects ( over 18 years old ) who were at high risk of developing the disease because of obesity , impaired glucose tolerance , impaired fasting glycaemia , or gestational diabetes .
the interventions : we considered dietary modifications or physical activity or both to prevent t2d or control obesity .
the comparison : any comparison arm or group used against the lifestyle intervention was accepted for this review .
outcomes : these were cost per qaly ( quality adjusted life years ) gained , cost per life year gained , cost per daly ( disability adjusted life years ) averted , cost per diabetes case averted , and other relevant outcomes .
studies that were published in english , french , or spanish . the first reviewer ( koffi alouki ) extracted data using a standardized data extraction form built according to the consolidated health economic evaluation statement ( cheers ) .
the second reviewer ( clara bermdez - tamayo ) checked that the extracts and discrepancies were resolved through discussion .
data extracted included the type of economic evaluation , subjects ' characteristics ( e.g. , age , biological and anthropometric characteristics ) , intervention details ( e.g. , duration , location , intensity , and mode of delivery of the intervention ) , comparator , analytical model used , effectiveness data , sensitivity analysis , and reported outcomes relevant to the review .
there are some trial - based type studies while others relied on model - based studies or previous trial results to extrapolate by using modeling techniques , something which was previously highlighted in the literature .
the interventions compared , the population groups targeted , and the outcomes reported also varied across studies . for these reasons we chose a narrative approach for this systematic review , as is usually done for systematic reviews of economic evaluations .
we used the british medical journal ( bmj ) quality assessment checklist , a 36-item scale , to assess the quality of the studies .
this checklist was developed with the aim of standardizing the presentation of study data , thereby contributing to the quality of economic evaluations .
we also assessed any risk of bias due to conflicts of interest or sponsorship of studies .
each item was answered by  no  or  yes  or  not applicable .
 we gave a score of 0 if the answer was  yes  and 1 if it was  no .  then we summed up the number of  no  responses to obtain a global score in which a higher score represented poorer quality .
two reviewers ( koffi alouki , clara bermdez - tamayo ) conducted this operation independently and disagreements were resolved through discussion . quality rating was used to interpret the results but no study was excluded on this basis .
the search yielded 176 abstracts . after reviewing the abstracts , subsequent reference tracking , and excluding duplicate articles , we narrowed the focus to 56 candidate studies having performed an original economic evaluation
. further review of the full text resulted in 20 studies that met our inclusion criteria .  
the studies were conducted in the uk , usa , canada , australia , germany , finland , the netherlands , singapore , sweden , and china .
three studies performed only a cost - effectiveness analysis while 13 studies assessed only cost - utility .
the four remaining studies combined cost - effectiveness and cost - utility analysis . there were 10 studies using a markov - type model or a decision tree , or both , to make projections of the evolution of t2d [ 2224 , 2629 , 31 , 33 , 35 ] .
the period for which the potential benefit of the intervention was simulated ranged from three years to lifetime .
the two studies targeting women with gestational diabetes were conducted throughout pregnancy [ 20 , 31 ] . in eight studies [ 16 , 17 , 22 , 23 , 25 , 2729 ] , data on efficacy and effectiveness used in simulations
were drawn from the major randomized controlled trials on t2d prevention : dppos , dpp , and da qing . in a further six studies , effectiveness data was based on synthesis of multiple studies [ 24 , 3135 ] .
six of the 20 studies used effectiveness data from a specific intervention conducted in the same country where the economic evaluation was carried out [ 1821 , 26 , 30 ] .
the cost to the healthcare system only or to the whole society was generally considered .
the costs and the effectiveness were discounted using rates varying from 3% to 5% according to the countries . to test the robustness of the results ,
it was not possible to identify the source of funding for only one study . among the other 19 studies ,
the interventions included in this review varied from the simple provision of information to active behaviour change schemes .
the lifestyle changes described across studies pertained to diet , physical activity , or both . in some cases , the screening of subjects at high risk preceded the interventions without explicitly taking account of the screening in the cost calculations [ 17 , 18 , 24 ] .
of 10 model - based studies , seven simulated interventions based on the dpp [ 2325 , 28 , 29 ] or the china da qing study [ 22 , 27 ] .
the dpp intervention goal was to achieve and maintain a weight reduction of at least 7% of initial body weight through diet and physical activity of moderate intensity , such as brisk walking for at least 150 minutes per week .
the dpp program included a lifestyle curriculum , taught by case managers on a one - to - one basis during the first 24 weeks after enrollment .
subsequent individual sessions ( usually monthly ) and group sessions with the case managers were designed to reinforce the behavioral changes .
the aim of nutritional counselling was to help the participants achieve a diet containing 10% of total energy intake as saturated fats , 510% as polyunsaturated fats , 2530% as total fat ( saturated , monounsaturated , polyunsaturated , and trans fatty acids ) , and 25 to 35 grams of fibre per day .
one study described a commercial program consisting of a low - calorie diet and physical activity advice .
one study carried out the economic evaluation of the  dash  diet ( dietary approaches to stop hypertension ) or a  low fat  diet   to reduce the disease burden related to excess body weight .
diet emphasizes reduced consumption of fat , red meat , sweets , and sugar - containing beverages , and the program recommends 180 minutes per week of moderate intensity physical activity .
one study performed the economic analysis of lifestyle changes achieved through e - learning devices .
another economic evaluation from the united kingdom was conducted on a program focusing on very low - calorie diets .
two studies reported on the economic evaluation of interventions consisting solely of physical activity [ 21 , 35 ] .
it took the form of a structured programme of exercise in a fitness centre and incorporating monitoring of individual performance .
the second study pertained to sessions of physical activity that included 60 minutes of walking in addition to exercise .
the exercise sessions consisted of aerobic and strength exercises . depending on the studies , the comparison ( or control ) interventions were common standard care , placebo , metformin ( 850  mg twice daily ) , or simple advice in writing for physical activity and nutrition . reported costs depended on the chosen perspective , the nature of the intervention , the target population , and the time horizon .
there is no consistency across studies in the items included to estimate the costs of interventions .
all studies considered direct costs including medical costs [ 16 , 17 , 2023 , 25 , 30 ] .
medical records were the most common source for data on diabetes and complications . generally , the direct medical costs were copayment fees for treatment , diagnostic testing , prescription drugs , and medical supplies .
the direct costs also included the costs of visits to healthcare providers and exercise physiologist and metformin cost for controls .
direct nonmedical costs pertained to services such as transportation of subjects and family members to clinics , as well as special food in some instances .
lost income for the patients and their families and the costs of hiring nurses or care providers were recorded as indirect costs .
four studies [ 18 , 20 , 21 , 23 ] reported on the estimated cost of productivity loss . in four of the 20 studies
[ 22 , 24 , 25 , 29 ] , cost estimates were only presented as category totals , without breakdown into individual items and without a separate presentation of the resources needed for the interventions .
two studies described the unit costs of various resources , using the ingredient approach [ 27 , 28 ] .
physical quantities of necessary inputs were counted and multiplied by unit prices to obtain total costs .
price data came from healthcare facilities , from patient records , or else from estimates based on published data .
seven studies recorded costs alongside the trials [ 1719 , 21 ] . except for four studies [ 1821 ] , all studies discounted the costs by 3% to 5% .
the effectiveness data were usually derived from major randomized controlled trials on t2d prevention [ 7 , 17 , 19 , 38 , 39 ] . nearly one - third of studies estimated effectiveness based on meta - analyses or literature reviews [ 24 , 3135 ] .
three out of the 20 studies reported effectiveness as dalys averted [ 24 , 31 , 33 ] .
diabetes cases averted by the interventions were reported in two studies [ 19 , 24 ] .
one study reported change in utility as an outcome measure , based on the 15-dimension questionnaire tool ( 15d ) to assess quality of life but without conversion to quality adjusted life years .
nine studies ( 9/20 ) used the eq5d ( euroqol 5-dimension tool ) , three studies used the qwb - sa ( quality of well being - self - administered ) , two studies used the hrqol ( health related quality of life ) system , one study used the vsa ( visual scale analog ) , and one study used the 15d or sf-36 ( 36-item short form survey instrument ) .
in some cases , the key assumption was that the expected effects of the intervention were for the short term with a linear decrease in effectiveness following the intervention .
another study projected the same effectiveness during the whole duration of the time horizon projected .
the probability of progressing from prediabetes to t2d in all studies using modeling techniques was always lower in the intervention arm consisting of lifestyle intervention than in the comparison arm , whether placebo , usual care , or metformin treatment .
assumptions regarding the effectiveness of screening were needed when screening was required before implementing interventions .
the studies reported sensitivity and specificity of screening ranging from 75% to 100% [ 22 , 25 ] .
compared with usual care , placebo , or metformin , interventions based on lifestyle modifications were reported as cost - effective in 15 of 20 studies [ 16 , 17 , 19 , 2230 , 3335 ] .
the conclusions are usually based on the incremental cost - effectiveness ratio as applied in the study countries .
one study considered the who threshold to decide on the cost - effectiveness , according to which intervention is considered highly cost - effective when the icer is below the gdp ( gross domestic product ) per capita and cost - effective when the icer ranges from 1 to 3 times gdp per capita .
when a strategy improves health outcomes at lower cost , it is considered to be dominant and it is obviously preferred as cost - effective .
those interventions that are less effective and more costly ( considered as dominated interventions ) or more costly and more effective but with a resulting more expensive icer would unlikely be cost - effective ; these studies were considered inconclusive .
three studies revealed that the interventions were dominant [ 17 , 22 , 27 ] .
oostdam et al .   reported that a lifestyle intervention implemented during 32 weeks and targeting at - risk pregnant women in germany was not cost - effective .
similar results were also reported in another intensive lifestyle intervention targeting at - risk pregnant women .
one study reported that a lifestyle intervention offered by nurses was not more cost - effective in reducing t2d risk than the control intervention consisting in the provision of a general health brochure .
johansson et al .   examined the cost - effectiveness of lifestyle by sex and concluded that intervention was only cost - effective among women .
sensitivity analysis , which allows assessing the reliability and the generalizability of the results , was performed in all studies except one .
over half the studies performed univariate sensitivity analysis and eight studies performed bivariate sensitivity analysis .
probabilistic sensitivity analysis was used in ten studies [ 18 , 21 , 24 , 2629 , 31 , 32 , 35 ] .
the input parameters that were analyzed through a range of assumed values were discounted cost and outcomes ( qalys gained ) , variations of intervention cost , variation of probability of transition between disease states considered , the duration of interventions , the size of the population at risk , and performance and frequency of screening test .
although the icer was sensitive to changes in the above parameters , it remained acceptable for most studies , except for the three studies reporting that the intervention was not cost - effective [ 20 , 27 , 31 ] . based on the bmj checklist , the studies included in this review showed quality limitations in reporting as shown in figure 2 .
out of the remaining 20 studies , 15 presented at least two methodological limitations and five studies showed only one .
more than half ( 12/20 ) of studies did not address the issue of generalizability .
the justification of the parameters used for the sensitivity analysis was presented by only few studies .
the models of five studies were not fully described or their choice was not justified .
eight studies did not report separately the resources for the interventions and their unit cost .
the purpose of this systematic review was to describe economic evaluations of lifestyle interventions to prevent t2d or control obesity in high - risk population groups and which were carried out since 2009 .
lifestyle interventions in communities and schools for the primordial prevention of t2d were excluded as a recent review reported on their cost - effectiveness .
our results confirmed those of former reviews [ 12 , 13 ] , which concluded that lifestyle interventions through physical activity or diet or combining both were generally cost - effective , with a few exceptions . in our review , five out of the 20 studies were inconclusive .
there was a trend for a higher proportion of interventions targeting the prevention of t2d compared to those focusing on obesity to be cost - effective ( 11/14 versus 4/6 , resp . ) .
the inconclusive studies [ 18 , 20 , 21 , 31 , 32 ] included one on the prevention of t2d , two on the prevention of gestational diabetes among pregnant women , and two on obesity control .
these studies were more costly with less effectiveness or more costly with higher effectiveness but resulting in a more expensive incremental cost - effectiveness ratio compared with standard care ( or control treatment ) .
three of the seven studies conducted within trial were nonconclusive compared with three of the 13 studies based on models .
the short duration of some studies may also explain the absence of significant changes in the outcomes .
another inconclusive study pertained to an e - based intervention , which may not induce enough motivation for change .
overall , there was considerable heterogeneity in the nature of lifestyle interventions across studies , which hampered comparisons and possibly contributed to the inconsistencies in outcome findings .
study results could be influenced by intervention components , selection of participants , and methodological and modeling choices .
few studies evaluated effectiveness in terms of qaly although it is known that diabetes is associated with deterioration of the quality of life .
qaly is a relevant parameter that allows comparisons of the burden of disease in terms of quality and quantity .
preference - based health state classification systems were preferred in most studies to objective methods of evaluation of health states .
mcdonough and tosteson   showed that , among studies that compared alternative preference - based systems , the eq-5d tended to provide larger change scores and therefore more favourable results than the health utility index ( hui ) , while the sf-6d provided smaller change scores and therefore less favourable ratios than the other systems .
hence , the choice of outcome as a measure of effectiveness has an impact on reported results .
cost variations were due primarily to the chosen perspective ( societal / health system or third party ) , to the various inputs for the interventions , and to differences of care unit costs across countries . the lifestyle interventions involved several health professionals , which explains the higher costs of these interventions compared to controls . in some but not all simulation studies , the costs of health infrastructure and training of personnel were also provided .
such inclusive costs would be particularly useful for low - resource countries where health systems are ill - prepared to tackle a chronic disease like t2d .
few studies complied with the recommendation to present quantity and unit cost of inputs separately from total cost as advocated in the guidelines , resulting in lack of the information required for the replication of the intervention in other settings . additionally , the reported costs were often incomplete .
for instance , if a societal perspective is adopted , the costs related to lost productivity , premature mortality , and permanent and temporary disability should be computed which is not always the case . as stated in the guidelines [ 47 , 48 ] , the future costs beyond one - year time should be discounted , which was done in most studies and using different discount rates .
although the selected rates were not justified in most studies , they probably reflect the fact that there are no universally accepted discount rates for economic evaluations studies .
the time horizon should be long enough to capture any significant difference between the intervention and the comparison groups in terms of costs and outcomes .
yet , it appeared too short in some studies to appraise and capture long - term impact of interventions .
particularly , in the management of obesity or gestational diabetes , the inconclusive results may be partly ascribed to too short interventions to capture the long - term benefits .
the costs for treating t2d complications are onerous , and the temporal horizon of some studies based on model assumptions can not guarantee that the complications will not appear later on .
however , without sustained compliance of subjects with advocated lifestyle changes , weight regain over the long - term can alter the quality of life and impinge on the estimated cost - effectiveness of interventions .
considering exclusively the short - term effects of obesity control interventions can indeed be misleading .
for this reason , it is not impossible that the cost - effectiveness of some interventions reviewed here and focusing on obesity was overestimated .
trial - based studies limited the results of interventions to health gains over the course of the intervention .
in contrast , studies supported by models were based on assumptions on a longer temporal horizon .
this approach , however , would omit taking into account other relevant events that may occur later on that will have an impact on the costs and on the quality of life or other outcomes .
additionally , the nature of the model inevitably has a bearing on the estimated cost - effectiveness of the interventions .
modeling diabetes evolution showed variations among studies with regard to the shift from normal glycaemia to prediabetes and then to diabetes and finally to the complications . with the exception of one study
, the models however seemed to be consistent with the natural evolution of the disease as described in the literature .
the accuracy of the models is one of the criteria for sound economic evaluations , and it reflects the ability to capture the evolution of the pathology in a real situation [ 51 , 52 ] . yet , in some studies , the models showed complication states without disclosing the nature of the complications .
another limitation of most models is that complications are taken separately into account while subjects living with t2d can have several complications .
some studies [ 23 , 25 ] did not consider the likelihood of glycaemia returning to normal in subjects with prediabetes .
the simplification of analytical models may not help to consider these subtleties during the course of evolution of the disease in a real situation .
most simulated interventions were based on epidemiological studies of t2d prevention that provide the reference evidence for lifestyle interventions as relevant strategy to prevent diabetes .
the randomized controlled trials that measured the long - term effects in real life situations after cessation of the active intervention [ 37 , 39 ] therefore provide important new data for the simulation studies to better estimate the long - term effectiveness of interventions to prevent diabetes . however , the efficacy observed in controlled experimental conditions is different from the expected effectiveness in the real world because of subject selection , recruitment , and follow - up and other factors that have a bearing on economic outcomes [ 10 , 53 ] .
moreover , in some model - based studies , the at - risk subjects may not accurately match the at - risk subjects of the original studies , so that the assumed effectiveness in these studies is uncertain .
the effectiveness of interventions in the real world often falls a long way short of the maximum efficacy shown in trials .
for instance , a retrospective observational analysis of overweight and obese subjects demonstrated that , compared with the 58% reduction in risk of progression to diabetes seen in the dpp trial , risk reduction for incident diabetes in subjects who participated in the study in an intense and sustained way was lower .
most articles lacked one or several reporting items of the bmj checklist for quality of economic evaluation studies although this checklist was issued before these studies were conducted .
another limitation observed is the lack of a clear description of the models , while the guidelines recommend transparency in their description . in some cases
, the models did not adequately capture the natural history of the disease , leading to questionable conclusions .
conversely , in another study , the model did not include the complication state , which would have been relevant in the natural history of diabetes .
however , although we performed an evaluation of the quality of studies , we deliberately chose not to exclude any study on that basis . in any case , excluding the poorer quality studies would not have altered the conclusions .
we used a comprehensive electronic search strategy using preestablished criteria in common medical literature databases .
as all studies are not referenced in electronic databases , we revisited the bibliography of each selected study to ensure that our search was exhaustive .
two reviewers cross - checked the database to identify the relevant studies . at variance with previous reviews on the economic evaluation of t2d prevention studies ,
ours also included intervention studies targeting obesity as main risk factor for t2d and not only the interventions aiming directly at t2d prevention .
ours also encompassed the assessment of study quality based on the bmj guidelines designed for the critical appraisal of economic evaluation studies .
we adopted a dichotomous scale for each item , however , which does not reflect the level of completeness of the information reported for each item considered .
it is also recognized that limiting the candidate studies to those published in french , english , and spanish is a potential source of publication bias . due to the heterogeneity in the methods and results of the different studies
, we were not able to perform a meta - analysis , which is usually considered the  gold standard  but which is not often feasible with economic evaluation studies .
the present review on the cost - effectiveness of lifestyle modification interventions showed , with only a few exceptions , that these interventions targeting adult subjects at high risk for diabetes were cost - effective despite different assumptions regarding disease progression and variations in the delivery of these interventions .
the results are consistent with conclusions of former reviews , confirming the importance of lifestyle interventions combining diet and physical activity to prevent diabetes in at - risk population groups .
this review also broke new ground by assessing the methodological limitations of the economic evaluations and the quality of reporting , to aid in interpretation of results .
lifestyle interventions should be further stressed as an effective strategy to prevent or delay diabetes .
unfortunately , few studies have been conducted in resource - poor countries in spite of a dire need for such data , and the findings from developed countries are not entirely relevant .
future research should address the effectiveness and cost - effectiveness of such interventions in low - income country settings , where the prevalence of t2d is soaring .
meanwhile , the data of the present review provide compelling arguments for policy makers to implement measures to prevent t2d .
 
 objective . to summarize key findings of economic evaluations of lifestyle interventions for the primary prevention of type 2 diabetes ( t2d ) in high - risk subjects 
 . methods . 
 we conducted a systematic review of peer - reviewed original studies published since january 2009 in english , french , and spanish . 
 eligible studies were identified through relevant databases including pubmed , medline , national health services economic evaluation , cinhal , econlit , web of sciences , embase , and the latin american and caribbean health sciences literature . 
 studies targeting obesity were also included . 
 data were extracted using a standardized method . 
 the bmj checklist was used to assess study quality . 
 the heterogeneity of lifestyle interventions precluded a meta - analysis . 
 results . 
 overall , 20 studies were retained , including six focusing on obesity control . 
 seven were conducted within trials and 13 using modeling techniques . 
 t2d prevention by physical activity or diet or both proved cost - effective according to accepted thresholds , except for five inconclusive studies , three on diabetes prevention and two on obesity control . 
 most studies exhibited limitations in reporting results , primarily with regard to generalizability and justification of selected sensitivity parameters . conclusion . 
 this confirms that lifestyle interventions for the primary prevention of diabetes are cost - effective . 
 such interventions should be further promoted as sound investment in the fight against diabetes . 
1. Background
2. Methods
3. Results
4. Discussion
5. Conclusion