General information
  • Disease category Mental and Behavioural diseases , Nutritional and Metabolic diseases (BASEC)
  • Study Phase N/A (ICTRP)
  • Recruitment status recruitment completed (BASEC/ICTRP)
  • Trial sites
    Basel
    (BASEC)
  • Contact PD Dr. med. Bettina Wölnerhanssen bettina.woelnerhanssen@claraspital.ch (BASEC)
  • Data Source(s) BASEC: Import from 10.02.2026 ICTRP: Import from 16.05.2026
  • Last update 16.05.2026 02:00
HumRes48341 | SNCTP000003593 | BASEC2019-02109 | NCT04234373

The importance of the gut-brain axis and the effect of a low-carbohydrate diet in overweight and depression

  • Disease category Mental and Behavioural diseases , Nutritional and Metabolic diseases (BASEC)
  • Study Phase N/A (ICTRP)
  • Recruitment status recruitment completed (BASEC/ICTRP)
  • Trial sites
    Basel
    (BASEC)
  • Contact PD Dr. med. Bettina Wölnerhanssen bettina.woelnerhanssen@claraspital.ch (BASEC)
  • Data Source(s) BASEC: Import from 10.02.2026 ICTRP: Import from 16.05.2026
  • Last update 16.05.2026 02:00

Summary description of the study

In this project, we will investigate the effects of a carbohydrate-reduced diet. Depressive disorders and overweight frequently occur together, and it is estimated that about one-third of all individuals with depression belong to the "metabolic", i.e., overweight subtype.
We are conducting this project to find out whether overweight and depressed patients can benefit from this dietary adjustment.

The study consists of a screening and 6 study days.
Through an application software (= "App", Application software), participants are trained and gradually adjust their diet until after about 2 months a maximum intake of 130g of carbohydrates per day is reached. Before and after this dietary change, which is to be maintained for a total of 6 months, numerous investigations are carried out. These include blood draws (vitamins and trace elements, blood fats, blood sugar, etc.), determination of body composition (fat percentage, muscle percentage), determination of liver fat percentage, and a functional examination of the brain using MRI (Magnetic Resonance Imaging), as well as stool samples to determine the composition of gut bacteria, questionnaires on gastrointestinal complaints and mental state.

(BASEC)

Intervention under investigation

The research project investigates the effect of a carbohydrate-reduced diet ("Low Carb") on metabolism and psyche.

(BASEC)

Disease under investigation

Overweight
Diabetes
Depression

(BASEC)

Criteria for participation in trial

This project is conducted in Switzerland (Basel) and Germany (Lübeck). In Switzerland, the following participants are included:

Control group:
Normal-weight individuals (i.e., BMI = Body Mass Index 19.0-24.9kg/m2), aged between 18 and 55 years and physically and mentally healthy (control group) or have depression (Depressed, Slim).

Overweight individuals:
Overweight individuals (i.e., BMI = Body Mass Index >30kg/m2), aged between 18 and 55 years and have elevated blood sugar levels (pre-diabetes or diabetes) without or with depression.

(BASEC)


Exclusion criteria

Individuals who cannot participate include those who:

  • are already on a carbohydrate-reduced diet or otherwise follow a special diet
  • suffer from a mental illness
  • regularly take stomach acid blockers
  • regularly take probiotics or prebiotics (bacterial preparations for the gut)

(BASEC)

Trial sites

Basel

(BASEC)

Switzerland (ICTRP)

Sponsor

St. Clara Research Ltd at St. Claraspital Basel

(BASEC)

Contact

Contact Person Switzerland

PD Dr. med. Bettina Wölnerhanssen

+41616858585

bettina.woelnerhanssen@claraspital.ch

St. Clara Forschung AG, Basel

(BASEC)

General Information

University Hospital, Basel, Switzerland,

0041616858585;0616858585

bettina.woelnerhanssen@unibas.ch; forschung@claraspital.ch

(ICTRP)

General Information

University Hospital, Basel, Switzerland

(ICTRP)

Scientific Information

University Hospital, Basel, Switzerland,

0041616858585;0616858585

bettina.woelnerhanssen@unibas.ch; forschung@claraspital.ch

(ICTRP)

Name of the authorising ethics committee (for multicentre studies, only the lead committee)

Ethics Committee northwest/central Switzerland EKNZ

(BASEC)

Date of authorisation

09.12.2019

(BASEC)


ICTRP Trial ID
NCT04234373 (ICTRP)

Official title (approved by ethics committee)
Understanding gut-brain interactions and the effect of a low-carb dietary intervention in obese and depressive patients with and without glucose intolerance or diabetes: a pilot trial (BASEC)

Academic title
Understanding Gut-brain Interactions and the Effect of a Low-carb Dietary Intervention in Obese Patients With and Without Glucose Intolerance or Diabetes: a Pilot Trial (ICTRP)

Public title
Effect of a Low-carb Dietary Intervention in Obese Patients: a Pilot Trial (ICTRP)

Disease under investigation

Glucose IntoleranceObesity

(ICTRP)



Intervention under investigation

Other: Low Carb diet

(ICTRP)



Type of trial
Interventional (ICTRP)

Trial design

Allocation: N/A. Intervention model: Single Group Assignment. Primary purpose: Treatment. Masking: None (Open Label).

(ICTRP)



Inclusion/Exclusion criteria

Inclusion Criteria:

Group A: HEALTHY LEAN CONTROLS

  • Healthy normal weight subjects with a body-mass index of 19.0-24.9kg/m2, HbA1C <5.7% and fasting glucose <5.6 mmol/l
  • Normal eating habits
  • Stable body weight for at least three months
  • Informed Consent as documented by signature

Group B: PRE-DIABETIC or DIABETIC OBESE

  • Pre-diabetic/Diabetic obese with a HbA1C >5.7% and/or fasting glucose >5.6 mmol/l) and body-mass index > 30kg/m2, otherwise healthy
  • Normal eating habits
  • Stable body weight for at least three months
  • Informed Consent as documented by signature

Exclusion Criteria:

Group A: HEALTHY LEAN CONTROLS

  • Pre-existing low carb diet (less than 45% of daily energy intake by carbohydrates)
  • Pre-existing diet (vegetarian, vegan, gluten-free etc.)
  • Psychiatric illness
  • Alcohol abuse, (smoking allowed)
  • Regular intake of medications, (oral contraceptives allowed)
  • Intake of antibiotics within the last 3 months before inclusion
  • Regular intake of pro- or prebiotics
  • Chronic diseases of the gastrointestinal tract, history of gastrointestinal surgery with major changes to the gastrointestinal tract (e.g. bariatric surgery)
  • Clinically relevant acute or chronic inflammatory disease
  • Pregnancy
  • Participation in another study with investigational drug within the 30 days preceding and during the present study.

Group B: PRE-DIABETIC or DIABETIC OBESE

  • Pre-existing low carb diet (less than 45% of daily energy intake by carbohydrates)
  • Pre-existing diet (vegetarian, vegan, gluten-free etc.)
  • Psychiatric illness
  • Alcohol abuse, (smoking allowed)
  • Regular intake of medications (except: oral contraceptives, metformin, SGLT-2, statins, and antihypertensive, which are allowed)
  • Intake of antibiotics within the last 3 months before inclusion
  • Regular intake of pro- or prebiotics
  • Chronic diseases of the gastrointestinal tract, history of gastrointestinal surgery with major changes to the gastrointestinal tract (e.g. bariatric surgery)
  • Clinically relevant acute or chronic inflammatory disease
  • Pregnancy
  • Participation in another study with investigational drug within the 30 days preceding and during the present study.

(ICTRP)



not available

Primary and secondary end points

Effect of a low-carb dietary intervention on glycemic control as defined by blood glucose level at 2h after an oral glucose tolerance test.

(ICTRP)



Effect of a low-carb dietary intervention on body composition as measured with dual-energy x-ray absorptiometry;Effect of a low-carb dietary intervention on metabolomics as measured in plasma, urine and stool samples;Effect of a low-carb dietary intervention on gut microbiota composition as measured in stool samples;Effect of a low-carb dietary Intervention on brain network activity as measured with functional MRI;Effect of a low-carb dietary intervention on liver fat fraction as measured with MRI

(ICTRP)



Registration date
not available

Incorporation of the first participant
not available

Secondary sponsors
not available

Additional contacts
Bettina W?lnerhanssen, MD;Bettina W?lnerhanssen, MD;Bettina W?lnerhanssen, MD, bettina.woelnerhanssen@unibas.ch; forschung@claraspital.ch, 0041616858585;0616858585, University Hospital, Basel, Switzerland, (ICTRP)

Secondary trial IDs
LCP Obese (ICTRP)

Results-Individual Participant Data (IPD)
not available

Further information on the trial
https://clinicaltrials.gov/study/NCT04234373 (ICTRP)

Results of the trial

Results summary

not available

Link to the results in the primary register

not available