The aim of this randomised controlled trial (RCT) is to investigate if prolonged consumption of sweetener and sweetness enhancers (S&SEs) within a healthy diet approach will improve weight loss maintenance and obesity related risk factors, and affect safety markers, compared to sugar.

We hypothesize, that:

• Prolonged use of S&SEs in beverages and food matrices will result in improved body weight control because S&SEs will increase palatability of the diet and thereby increase compliance to the recommendations for a healthy diet.
• There will be no safety concerns using S&SEs in the long term.

Overweight/obese adults and families where at least one adult (both gender) and one child (both gender) are overweight/obese will be recruited. The majority of measurements will only be conducted in the adult population and some measurement will only be done in sub-groups. The intervention will be performed in four countries: Denmark, Greece, Spain and the Netherlands.

The goal is approximately 370 participants - 330 adults (18-65 years of age) and 40 children (6-12 years of age) - will be recruited for the study. All adult participants are first treated by a low energy diet (LED) for 2 months with the aim to reduce body weight (minimum 5% weight loss (WL)), whereas children are treated separately with a conventional weight maintenance (WM) diet, without a specific aim for absolute WL.

The participants - both adults and families - are randomized into two different diet interventions for 10 months with or without inclusion of S&SEs products (foods and drinks). For adults, this period aims at preventing weight re-gain and for children maintaining body mass index (BMI)-for-age. The participants will receive food exchange lists and will be guided by dieticians. The randomization will be stratified by age, sex and BMI. Adults (not participating with children) belonging to the same household and all members of a family will be assigned the same intervention - the randomization will here solely be based on the oldest adult in the family/household.

The adult participants are weighed at months 0, 0.5 and 1, and if needed at month 1.5. They are supervised during the WL period at months 0 and 1, and if needed at months 0.5 and 1.5, and throughout the WM period at months 2, 4, 6, 9 and 12. Children will follow a similar, but less strict time schedule (their participation is preferred but not required for all dietician meetings).

The main assessment points are the clinical investigation days (CIDs) at month 0 (baseline, start of the WL period), 2 (end of the WL period/start of randomized intervention), 6 (6 months from baseline) and 12 (1 year from baseline).

Inclusion criteria for adults:

• Age: 18-65 years.
• BMI: ≥25.0 kg/m2 (no upper limit). For women: Use of contraceptive methods and not wishing/planning to become pregnant in the 1 year of the intervention study.
• Regular consumption of sugar-containing/sugar-sweetened products.
• Able to participate in CIDs and dietician meetings during normal working hours.
• Motivation and willingness to be randomized to any of the two groups and to do the best to follow the given protocol.

Inclusion criteria for children:

• Age: 6-12 years.
• BMI-for-age: >85th percentile (no upper limit).
• Able to participate in CIDs during normal working hours.
• Motivation and willingness to be randomized to any of the two groups and to do the best to follow the given protocol.

Exclusion criteria for adults:

• Weight change (increase or decrease) >5% during the past 2 months prior to the study.
• Surgical treatment of obesity.
• Blood donation < 3 month prior to study.
• Change in smoking habits during the last month. Smoking is allowed provided subjects have not recently changed habits. However, smoking status is monitored throughout the study and used as a confounding variable.
• Regularly drinking >21 alcoholic units per week (men), or >14 alcoholic units/week (women).
• Intensive physical training (>10 hours of per week).
• Self-reported eating disorders.
• Intolerance and allergies expected to interfere with the study.
• Self-reported drug abuse within the previous 12 months.
• Night- or shift work that ends later than 11 PM.
• For women: Pregnancy, lactation.
• Persons who do not have access to either (mobile) phone or internet (this is necessary when being contacted by the study personnel during the study).
• Insufficient communication with national language.
• Inability, physically or mentally, to comply with the procedures required by the study protocol as evaluated by the daily study manager, site-PI, PI or clinical responsible
• Participant's general condition contraindicates continuing the study as evaluated by the daily study manager, site-PI, PI or clinical responsible.
• Simultaneous participation in other clinical intervention studies.

Medical conditions as known by the persons:

• Diagnosed diabetes mellitus.
• Medical history of CVD (e.g. current angina; myocardial infarction or stroke within the past 6 months; heart failure; symptomatic peripheral vascular disease).
• Systolic blood pressure above 160 mmHg and/or diastolic blood pressure above 100 mmHg (measured at screening) whether on or off treatment for hypertension.
• Significant liver disease, e.g. cirrhosis (fatty liver disease allowed).
• Malignancy which is currently active or in remission for less than five years after last treatment (local basal and squamous cell skin cancer allowed).
• Active inflammatory bowel disease, celiac disease, chronic pancreatitis or other disorder potentially causing malabsorption.
• Thyroid diseases, except those on Levothyroxine treatment of hypothyroidism if the person has been on a stable dose for at least 3 months.
• Psychiatric illness (e.g. major depression, bipolar disorders).

Medication:

• Use currently or within the previous 3 months of prescription or over the counter medication that has the potential of affecting body weight incl. food supplements. Except: low dose antidepressants if they, in the judgement of the daily study manager, site-PI, PI or clinical responsible, do not affect weight or participation to the study protocol. Levothyroxine for treatment of hypothyroidism is allowed if the person has been on a stable dose for at least 3 months.
• Cholesterol or blood pressure lowering medication, if the dose has changed during the last 3 months (i.e. the medication is allowed if the participant has been on a stable dose for at least 3 months).

Laboratory screening:

If all of the above criteria are satisfied, the adult participant is eligible for a laboratory screening. A blood sample is collected and immediately analysed for glucose and haemoglobin concentrations (Haemocue).

• Glucose ≥ 7.0 mmol/L.
• Haemoglobin concentration below local laboratory reference values (i.e. anaemia).
• Or any other significant abnormality on these tests which in the investigators opinion may be clinically significant and require further assessment.

After WL period (CID2, Month 2):

Failure to reach at least 5% weight reduction during the WL period (Months 0-2). This leads to exclusion from the WM intervention

Exclusion criteria for children:

• Intensive physical training (>10 hours of per week).
• Self-reported eating disorders.
• Intolerance and allergies expected to interfere with the study.
• Insufficient communication with national language.
• Inability, physically or mentally, to comply with the procedures required by the study protocol as evaluated by the daily study manager, site-PI, PI or clinical responsible.
• Subject's general condition contraindicates continuing the study as evaluated by the daily study manager, principal investigator or clinical responsible.
• Simultaneous participation in other clinical intervention studies.

Medical conditions as known by the child and the representative adult:

• Diagnosed diabetes mellitus.
• Other diseases that may influence the study outcomes as evaluated by the daily study manager, site-PI, PI or clinical responsible.

Medication:

• Use currently or within the previous 3 months of prescription or over the counter medication that has the potential of affecting body weight.

All data will be collected in a central DataHub at University of Copenhagen. First, the pseudo-anonymised individual participant data (IPD) are to be shared between (WP3-) relevant SWEET partners within the SWEET consortium via a data processor agreement (DPA). Second, the pseudo-anonymised IPD will be made available upon request before 2032 via a data sharing contract. Third, from 2032 (10 years after LPLV) fully anonymised data can be transferred."

See above in the plan description.

See above in the plan description.