Following a request from the European Commission, the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) was asked to deliver a scientific opinion on the essential composition of total diet replacements for weight control. Total diet replacements for weight control are intended to induce a substantial energy deficit in overweight or obese adults who […]
Following a request from the European Commission, the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) was asked to deliver a scientific opinion on the essential composition of total diet replacements for weight control. Total diet replacements for weight control are intended to induce a substantial energy deficit in overweight or obese adults who wish to lose weight and replace the whole diet in the context of energy-restricted diets for weight reduction.
The guiding principle for providing advice on the essential composition of total diet replacements for weight control should be that products are safe and suitable when consumed as a sole source of nutrition for several weeks to months by overweight or obese adults in the context of energy-restricted diets for weight reduction. In order to avoid nutrient deficiencies, these products should, therefore, provide at least the Population Reference Intake or the Adequate Intake for adults of all indispensable nutrients. As Dietary Reference Values are generally established for healthy, normal-weight individuals, specific consideration has been given by the Panel in this opinion whether there was an increase in nutrient requirements in the overweight or obese or (rapid) weight loss leads to an increased nutrient loss and thus a higher requirement. The Panel also considered the extent to which different diet compositions impact on losses in fat-free mass, and on other adverse effects of weight loss diets, such as gallstone formation. The effectiveness of a product in terms of extent of weight loss was not in itself considered an appropriate determinant for the necessary composition of total diet replacements for weight control.
The Population Reference Intake of 0.83 g/kg body weight per day cannot be directly applied to overweight or obese individuals considering that the Population Reference Intake was derived for healthy, normal-weight individuals with corresponding body composition. It is established that protein requirements are closely linked to fat-free mass and that in the overweight or obese the percentage of fat-free mass related to whole body weight is lower than in normal-weight persons because of a higher percentage of fat mass in relation to body weight. Accordingly, protein requirements for the overweight or obese should be related to fat-free mass. As both protein requirements and resting energy expenditure are mainly related to fat-free mass, the Panel proposes to correct the Population Reference Intake established for a normal-weight person by the quotient of the resting energy expenditure of overweight or obese individuals and the resting energy expenditure of a normal-weight reference subject. This correction translates into a minimum quantity of 75 g high-quality protein (i.e. Protein Digestibility-Corrected Amino Acid Score of 1.0) per day, which should be provided by total diet replacements for weight control. The value is supported by results from nitrogen balance studies, which have shown that obese subjects tended to return closer to nitrogen equilibrium, and somewhat faster, when 70‑100 g protein per day was consumed as part of an energy-restricted diet than when smaller amounts of protein were consumed. It is also supported by results showing that protein turnover is either maintained or only slightly decreased during caloric restriction provided a quantity of protein of between 50 g and 100 g/day is supplied in the diet.
With respect to the maximum protein content of total diet replacements for weight control, the Panel proposed to derive it from the maximum protein intakes considered as safe (i.e. equal to twice the Population Reference Intake) for an overweight 40-year-old woman with a body mass index of 25 kg/m2. This derivation results in a maximum quantity of 105 g protein per day in total diet replacements for weight control. This value is similar to the highest protein intakes investigated in the published studies with no apparent adverse effects.
Some studies seem to indicate that with a high protein supply of 100 g/day carbohydrates are not needed to achieve the desired effect of near-neutral nitrogen balance. However, the absence of carbohydrates in total diet replacements for weight control may carry a higher risk of severe ketoacidosis. Other studies on very low-calorie diets providing ≤ 2 510 kJ (600 kcal) per day with a lower protein intake, of between 50 and 70 g/day, and supplying carbohydrates in amounts of around 70 g/day have indicated that these intakes are of advantage with respect to nitrogen loss compared with a carbohydrate supply of around 10 g/day. Considering that up to 80 % of the energy requirement of the brain of around 2 092 kJ/day (500 kcal/day) can be supplied by ketone bodies, there remains a demand for, about 25‑30 g of glucose that can be produced via gluconeogenesis from glycerol and amino acids or be supplied by the diet. In order to keep the need for gluconeogenesis low, the Panel proposed a minimum content of digestible carbohydrates of 30 g/day.
Owing to the lack of scientific evidence, the Panel considered that an absolute minimum requirement for fibre in overweight and obese subjects during weight loss cannot be established, the more so as both constipation and diarrhoea have been reported during the use of total diet replacements. Therefore, the Panel cannot propose a minimum dietary fibre content in total diet replacements for weight control.
Although the addition of essential fatty acids to total diet replacements for weight control may not be needed owing to their release from tissue stores during weight loss, the Panel considered that total diet replacements for weight control should provide at least the Adequate Intake for linoleic acid and α‑linolenic acid established for energy-adequate diets. This recommendation is based on the consideration that the fatty acid content of adipose tissue and the rate of adipose tissue loss may vary between individuals; thus, there is considerable uncertainty as to whether body stores can completely cover requirements. Therefore, the Panel proposed that total diet replacements for weight control should provide at least 11 g linoleic acid and 1.4 g α‑linolenic acid per day.
The available evidence is insufficient to establish a minimum fat content in total diet replacements for weight control beyond their content of essential fatty acids. The above proposed minimum content of linoleic and α‑linolenic acid leads to a minimum amount of total fat provided by total diet replacements for weight control of around 20 g/day, as oils used to supply these fatty acids have a maximum essential fatty acid content of 55‑75 % of total fatty acids.
There is no evidence for proposing a maximum fat content in total diet replacements for weight control.
The minimum energy content of total diet replacements for weight control can be derived from the minimum macronutrient content of such diets. Considering that the Panel proposed that total diet replacements for weight control should provide at least 75 g protein per day, 30 g carbohydrates per day and linoleic and α‑linolenic acid in amounts which sum up to around 20 g fat per day, a minimum energy content of 2 510 kJ (600 kcal/day) could be derived.
From a scientific point of view, there is no evidence to establish a threshold below which a diet could be considered to be very low in energy content.
The minimum content of micronutrients in total diet replacements for weight control has generally been derived by the Panel from the Population Reference Intakes or Adequate Intakes for micronutrients based either on previous opinions of the Panel or in the absence of such advice on reference values given by the Scientific Committee on Food or other scientific or authoritative bodies. For none of the micronutrients was it considered that there was an increase in nutrient requirements in the overweight or obese or an increased requirement owing to rapid weight loss induced by total diet replacements for weight control when consumed for a single short period of time.
Conditions and restrictions of use
The Panel emphasises that the compositional advice given in the present opinion solely applies to total diet replacements for weight control which are to be used by otherwise healthy overweight or obese adults with the intention of weight loss. They are not intended for use in normal-weight adults, infants, children, adolescents, pregnant or lactating women and the elderly. They may also not be appropriate for overweight or obese populations with one or more medical conditions, such as, but not limited to, diabetes, gout, thyroid disease, kidney disease, liver disease, cardiovascular disease and gallstones. The appropriateness of the use of total diet replacements for weight control by individuals other than overweight or obese adults, such as obese adolescents or obese pregnant women, or by individuals with a medical condition, should be established on a case-by-case basis by a physician and may require continued medical and dietetic supervision.
The Panel noted that there is no scientific evidence which supports the current provisions that labelling of low-calorie diets should inform consumers that low-calorie diets should not be used for more than three weeks without medical supervision. However, none of the studies which investigated adverse metabolic consequences of total diet replacements had a duration of more than three months. In particular, studies which investigated critical endpoints, such as the effect of total diet replacements for weight control on calcium loss and bone health, have not been conducted for periods longer than eight weeks. While the available evidence does not give rise to any concern with respect to bone health in adults when total diet replacements for weight control are consumed for a single period of up to eight weeks, there are no data on the impact of the increased calcium losses on bone health when these products are used over prolonged periods of time or repeatedly for short periods. In addition, the compositional advice given by the Panel is based on the assumption that total diet replacements for weight control are used for a single short period of time and the nutrient content may not necessarily be appropriate when these products are consumed for prolonged or repeated short periods of time.
Finally, the Panel also noted the importance of an adequate fluid intake during energy restriction in line with the Adequate Intakes for adult men and women, i.e. 2.5 L and 2.0 L/day, respectively. The reference values for total water intake include water from drinking water, beverages of all kind and from food moisture.