Protein-rich foods may improve brain insulin-sensitivity, which is important for cognitive and metabolic health, and may also translate into an improved food intake regulation. It is therefore pertinent to delineate the effects of plant-derived proteins, which are a more sustainable alternative to animal-derived proteins, on brain insulin-sensitivity and related functional benefits. The hypothesis is that daily plant-derived or animal-derived protein supplementation improves brain vascular function and insulin-sensitivity, thereby improving cognitive performance and appetite control in overweight or obese older men and women.

The primary objective is to investigate in overweight or obese older adults the effect of daily protein supplementation for two weeks with either a plant-derived protein or an animal-derived protein on vascular function and insulin-sensitivity in the brain, while changes in cognitive performance and appetite-related brain reward activity will also be evaluated (secondary study objectives). Cerebral blood flow responses before (brain vascular function) and after the administration of intranasal insulin spray (brain insulin-sensitivity) will be quantified by the gold standard magnetic resonance imaging (MRI)-perfusion method Arterial Spin Labeling (ASL).

Inclusion Criteria:

• Men and women, aged between 60-75 years (older adults)
• BMI between 25-35 kg/m2 (overweight or obese)
• Fasting plasma glucose < 7.0 mmol/L
• Fasting serum total cholesterol < 8.0 mmol/L
• Fasting serum triacylglycerol < 4.5 mmol/L
• Systolic blood pressure < 160 mmHg and diastolic blood pressure < 100 mmHg
• Stable body weight (weight gain or loss < 3 kg in the past three months)
• Willingness to give up being a blood donor from 8 weeks before the start of the study, during the study and for 4 weeks after completion of the study
• No difficult venipuncture as evidenced during the screening visit

Exclusion Criteria:

• Intolerant to milk products or fava bean allergy
• Vegetarians
• Left-handedness
• Current smoker, or smoking cessation < 12 months
• Diabetic patients
• Familial hypercholesterolemia
• Abuse of drugs
• More than 3 alcoholic consumptions per day
• Use of products or dietary supplements known to interfere with the main outcomes as judged by the principal investigators
• Use medication to treat blood pressure, lipid, or glucose metabolism
• Use of an investigational product within another biomedical intervention trial within the previous 1-month
• Severe medical conditions that might interfere with the study, such as epilepsy, asthma, kidney failure or renal insufficiency, chronic obstructive pulmonary disease, inflammatory bowel diseases, auto inflammatory diseases, and rheumatoid arthritis
• Active cardiovascular disease like congestive heart failure or cardiovascular event, such as an acute myocardial infarction or cerebrovascular accident
• Contra-indications for MRI imaging (e.g., pacemaker, surgical clips/material in body, metal splinter in eye, claustrophobia)