In translating the evidence into recommendations, the NUGAG Subgroup on Diet and Health assessed the evidence in the context of the certainty in the evidence, desirable and undesirable effects of the interventions, the priority of the problem that the interventions would address, values and preferences related to the effects of the interventions in different settings, the feasibility and acceptability of implementing the interventions in different settings, the potential impact on equity and human rights, and the cost of the options available to public health officials and programme managers in different settings.
Because the recommended “interventions” in this guideline are in fact dietary goals, they can be translated into policies and actions in a number of ways, including behaviour change interventions, fiscal policies, regulation of marketing, labelling schemes and reformulation of manufactured products, among others. Because each of these interventions has its own substantial evidence base (which was not reviewed by the NUGAG Subgroup on Diet and Health) and requires individual consideration of the additional evidence to recommendation factors, a detailed discussion of these factors for each of the possible interventions is beyond the scope of this guideline. However, forthcoming WHO guidelines will provide specific guidance on nutrition labelling policies, policies on marketing of food and non-alcoholic beverages to children, fiscal and pricing policies, and school food and nutrition policies, which will enable policy-makers to translate dietary goals into evidence-informed policies.1 Therefore, in assessing the factors relevant to translating the evidence into recommendations for this guideline, the NUGAG Subgroup on Diet and Health primarily considered each recommendation in the context of achieving the recommended dietary goals.
Evidence for this process was gathered via comprehensive searches of relevant scientific databases and identification of high-quality studies, including recent systematic reviews, where available. An evidence to recommendation table can be found in Annex 7.2
Overall certainty in the evidence
The certainty in the effects for body weight, BMI and waist circumference was assessed as high, and for percentage of body fat as moderate. Because beneficial effects were observed for all outcomes, the overall certainty was assessed as high. There was high certainty in the evidence for all outcomes related to potential undesirable effects, except for quality of life, which was as assessed as low. Because no undesirable effects were observed, the overall certainty was as assessed as high.
Balance of desirable and undesirable effects
Although the effects observed for body measures of body fatness were small to modest in magnitude, they were highly significant and resistant to sensitivity analyses. No undesirable effects were observed as measured by blood lipids, blood pressure and quality of life; in fact, small improvements were observed for total cholesterol, LDL cholesterol and blood pressure. The effect observed for body fatness is expected to make a positive impact on unhealthy weight gain, particularly when paired with other healthy diet and lifestyle interventions. Therefore, as reviewed directly in this body of evidence, the desirable effects strongly outweighed the non-existent undesirable effects. However, the NUGAG Subgroup on Diet and Health acknowledged that some individuals who reduce their fat intake might replace some of the energy from dietary fat with energy from foods that are undesirable from a dietary quality perspective, such as free sugars (69), reducing the net benefit.
Conversely, because some foods containing significant amounts of fat are also high in sugars or sodium or are otherwise consumed alongside other unhealthy foods, the undesirable effects of not following the recommendation for total fat intake may be compounded by undesirable effects (not necessarily limited to unhealthy weight gain) resulting from the accompanying higher intakes of sugars, sodium and unhealthy foods in general. Unhealthy eating patterns have been documented in many settings and pose a significant and growing public health problem, particularly in many LMICs (70). It was also noted that reducing total fat intake might lead to undesirable effects in those who are undernourished. Therefore, special consideration must be given to undernourished individuals and in some such cases the recommendations may not be appropriate. However, in the general population it was felt that the balance between desirable and undesirable effects favours the intervention.
Priority of the problem and values and preferences
These recommendations address overweight and obesity by way of unhealthy weight gain. Overweight and obesity are highly prevalent and increasing globally, particularly in LMICs (15–17); therefore, interventions to prevent unhealthy weight gain are valuable in all contexts and preventing unhealthy weight gain is a high priority for many countries. Despite the rising global prevalence of overweight and obesity, the priority placed on this problem by national authorities may vary depending on the real or perceived magnitude of the problem within each country. However, in the context of the COVID-19 pandemic, the importance of prevention of overweight and obesity has been highlighted because there is increasing recognition of obesity as an important, independent prognostic factor and COVID-19 patients with obesity are at increased risk for adverse outcomes (71).
The recommendations in this guideline place a high value on reducing unhealthy weight gain because it may contribute to reducing the prevalence of overweight and obesity, which will not only increase the risk of various NCDs, but also the severity of COVID-19. While individuals almost universally value the prevention of premature mortality, those that may be affected by the recommendation may value the benefit of reducing risk of obesity and associated disease differently based on personal preferences, beliefs and customs. For example, because CVDs are a high profile public health topic, including in many LMICs where they represent a growing threat (72), it is expected that most individuals would value efforts to reduce risk; however, in real-world settings, perception of the risk varies considerably (73–77) and may require outreach and communication efforts to improve understanding. Similarly, although many people in LMICs are increasingly aware of the negative health effects associated with being overweight or obese, some cultures still consider overweight to be a desirable or positive attribute (78–80). Others believe body weight to be hereditary and therefore not amenable to management via lifestyle changes (77, 81). And many, regardless of personal beliefs, incorrectly perceive their own body weight in the context of overweight and obesity (i.e. they believe they are at a healthy body weight when in fact they are overweight or obese according to accepted standards for assessing body weight outcomes) (77, 81, 82).
Feasibility
In settings where efforts to reduce total fat intake are planned or are already underway, feasibility should be much higher than in settings where plans are not yet in place. Regardless, feasibility will be influenced by the existing, relevant infrastructure (for different interventions) and resources available. In terms of implementing interventions to affect the desired change in total fat intake (e.g. behaviour change and education campaigns, fiscal policies, marketing and labelling policies, and reformulation), feasibility will vary widely and detailed discussions of feasibility for each are beyond the scope of this guideline.
Relevant to all interventions, widespread use and availability of certain food items high in fat may pose challenges in decreasing consumption where necessary to meet the recommended intake. Regardless of which interventions are employed to realize the recommended fat intake, some amount of behaviour change at the individual level will be required. This may be challenging in some settings, particularly those in which popular opinion has currently been shaped to view high fat intake as healthy, particularly with respect to losing weight or maintaining a healthy body weight (83).
Acceptability
The recommendations in this guideline are in line with many existing national dietary guidelines and policies, however, acceptability may vary across different countries and cultural contexts.
Acceptability may be influenced by:
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how the recommendations are translated into policies and actions (e.g. nutrition labelling policies, marketing policies, fiscal policies, reformulation, etc.) because some may be more acceptable than others;
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level of awareness of the health problem that overweight and obesity pose (e.g. it may be less acceptable in settings where awareness is low);
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potential impact on national economies; and
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compatibility with existing policies.
At an individual level, for those who acknowledge the evidence linking total fat intake to unhealthy weight gain and value reducing the risk of unhealthy weight gain, acceptability should be high because overweight and obesity are a significant, recognized global health problem. As noted with respect to feasibility, however, there are many for whom the recommendation will not be acceptable based on the popular perception that high fat diets are healthy, particularly with respect to losing weight or maintaining a healthy body weight (83).
Equity and human rights
The recommendations in this guideline have the potential to reduce health inequity by improving the health of those of lower socioeconomic status because they are generally disproportionately affected by overweight and obesity. However, the effect on equity and human rights will probably be affected by how the recommendations are translated into policies and actions (e.g. fiscal policies and reformulation). The impact of some previously mentioned interventions on the pricing of manufactured foods would require careful consideration, because any increase in costs borne by manufacturers might be passed on to the consumer, which would be likely to disproportionately affect those of lower socioeconomic status.
In addition, a reduction in total fat intake may have different impacts on diets depending on what the nature of the dietary fat is in average diets in different settings. For example, in some settings, dietary fat may consist largely of unsaturated fatty acids and a reduction in total fat intake may have an impact on body weight but not CVDs. In settings where dietary fat consists largely of saturated fatty acids or trans-fatty acids, a reduction in total fat intake may have an impact on both body weight and CVDs. Because saturated fatty acids and trans-fatty acids may make up a larger percentage of total fat intake in some LMICs (84), in those settings reducing total fat intake might result in health benefits both in terms of body weight and cardiovascular health.
Resource implications
Costs of translating the recommendations into polices and actions will vary widely, depending on which approaches are taken, but will probably be associated with long-term savings in costs of health care. The extent of these savings and resource use depends on the strategies chosen for implementation and the timescale for evaluation. Implementation of the recommendations will probably require consumer education and public health communications, some or all of which can be incorporated into existing public health nutrition education campaigns and other existing nutrition programmes at the global, regional, national and subnational levels.
- 1
- 2
Evidence to recommendation information is summarized in this section only for recommendation 1. Evidence to recommendation information for recommendation 2 can be found in the WHO guideline Saturated fatty acid and trans-fatty acid intake for adults and children (68).
