The current study aims to investigate the cognitive effects of diet-induced blood glucose fluctuations on cognitive performance in healthy older adults over multiple days, taking advantage of the currently available techniques to continuously measure blood glucose levels and to assess cognitive performance in a real-life setting.

In this fully decentralized study, subjects will undergo two times a three-day measurement period, where their blood glucose will be continuously measured by a minimally invasive sensor and where the cognitive performance is measured at multiple time points throughout a day using a short test battery administered on their mobile phone. In addition to receiving standardized breakfast and lunch meals, the subjects are administered a low-GI(Glycemic Index) or normal-GI(Glycemic Index) snack in the morning and afternoon.

The study has two main scientific objectives. First, the investigators aim to investigate the acute effect of a low versus high-GI snack taken mid-morning or mid-afternoon on cognition, appetite, alertness and mood. To this end the investigators will compare the pre-snack and ~2-hour snack measurements of the two snacks. The investigators hypothesize that the low-GI(Glycemic Index) snack, due to a blunted and sustained PPGR, leads to better cognition, appetite and alertness ratings. Secondly, the investigators aim to explore how daily fluctuations in blood glucose are associated with cognition, mood, appetite and alertness in healthy older adults. To this end the investigators will conduct exploratory correlational analyses between blood glucose parameters, the behavioural outcomes, and subject characteristics.

Inclusion Criteria:

• Aged 50 - 65 years
• Own and use a smartphone that is capable to run the study applications (Android 4.4 or later, OS 12.0 or later)
• Adequate fluency in the English language to understand the inform consent process, study instructions and study assessments
• Sufficient vision and hearing to complete study procedures based on medical judgment
• Willing and able to participate and to give written consent to comply with study procedures

Exclusion Criteria:

• Presence or history of a metabolic, neurological, or psychiatric disease
• Use of prescription or OTC medication that may influence gastrointestinal, metabolic or neurological functioning
• Any health, functional or lifestyle factor that in the judgement of the investigator may interfere with the ability to comply with study procedures and/or the generation of valid study data
• Known food allergies
• Use of illicit drugs
• Alcohol intake >1 units/day • BMI <18.5 or >30 kg/m²
• Are a member of the research team or their immediate family members. Immediate family member is defined as spouse, parent, child, or sibling, whether biological or legally adopted

The randomization list will be prepared by an independent staff who is not part of the current study. A non-speaking code will be used for each of the snack types. The study team members will be kept blinded to the order of snack given to the participant