Type 2 diabetes mellitus (T2DM) is a metabolic disease with a rapidly increasing incidence world-wide. The disease is characterizedby a decreased glucose tolerance as a result of insulin resistance, resulting in poor blood glycaemic control. Blood glucose loweringmedications are widely available, but their effect stagnates as T2DM progresses. New treatment regimens are required to combatthe disease. Although therapies such as physical exercise have been shown to induce beneficial effects on glycaemic control inT2DM patients, not all patients are able to perform exercise. Passive heating treatment (PHT) might be an alternative strategy toreduce insulin resistance, as it has been postulated to have comparable effects on the cardiovascular system as exercise. PHT hasbeen linked to numerous health benefits, including improved cardiovascular- and pulmonary function, pain alleviation and metabolichealth. In addition, long term use of PHT shows promising effects on glycaemic control in T2DM patients. However, the acute effectsof PHT on glucoregulation are yet to be determined. Therefore, in this study we will assess the acute impact of passive heat treatment on the post-prandial glycaemic response during an OGTT in T2DM patients

Inclusion Criteria:

• Aged ≥50 years old
• Body mass index 18.5 - 35 kg/m2
• DM type 2
• Using oral blood glucose lowering medication
• Able to give informed consent

Exclusion Criteria:

• Insulin dependence
• Changes in diabetes medication in the past 3 months
• Allergy for one of the food items used
• >5% weight change in the previous 6 months
• Participating in a structured (progressive) exercise program, or in the past 3 months.
• Frequent (once per week or more) user of infrared (or traditional) sauna in the past 3 months
• Inability to tolerate sauna/high temperatures
• Smoking
• Diagnosed with cardiovascular disease (e.g. unstable angina pectoris or recent myocardial infarction), kidney failure (eGFR < 60 ml/min/1.73m2), rheumatoid arthritis
• Diagnosed musculoskeletal, GI tract, metabolic (except diabetes) or pulmonary (e.g. COPD) disorders that are expected to influence study outcomes
• Having a pacemaker, defibrillator, or any other type of metal implant

In this trial, neither the participants, nor the researchers who perform the trial days will be blinded to the intervention allocation. However, the researchers performing the blood analysis are blinded to the treatment allocation and are not involved in the research study during the trial days.