A randomized, open-label study with antacid-control will be performed over 48 hours period by continuous pH impedance and bravo capsule monitoring. Asymptomatic obese patients will be separated into either groups according to alginate antacid group [Gaviscon Advance (GA)®, Reckitt Benckiser, UK] and non antacid alginate group [simple antacid]. Both groups will be studied for 48 hours using the ambulatory wireless capsule and pH impedance. Participants according to their group will take either alginate antcid [Gaviscon Advance (GA)®, Reckitt Benckiser, UK] or non alginate antacid [simple antacid] which has equivalent strength of antacid after taking late night standardised meals.

Gastroesophageal reflux disease (GERD) with symptoms of heartburn and acid regurgitation is a common disorder especially in overweight and obese persons who are at increased risk for GERD. Late night supper, an usual eating habit in many parts of the world, may worsen GERD and especially so among the obese, and this may be due to increased reflux from acid pocket.

Acid pocket in the proximal part of stomach after meals has been shown to be an important mechanism of GERD. The acid pocket is increasingly recognized as a source from which acid reflux events originate. To what extent changes in acidity of the acid pocket contribute to the therapeutic effect of alginate antacid formulation is inconsistent. The other findings suggested that the main mechanism of action for the alginate-antacid combination is to displace the post-prandial acid pocket rather than mechanically containing it.

Therefore, the outcomes of the study will allow us to determine whether late night supper worsen acid pocket, night time reflux and symptoms and whether an alginate antacid preparation (Gaviscon Advance®) is useful in suppression of acid pocket, night time refluxes and symptom (s). A benefit is that this study may inform doctors and advise participants of GERD side-effects of late night supper and how Gaviscon Advance may help.

Inclusion Criteria:

1. Aged greater than or equal to 18 years and less than or equal to 70 years.
2. BMI >27.5 (based on kg/m2)

4. Not taking acid suppressant PPI and H2 receptor blockers 5. Not taking antacids or alginate preparations, except those administered as part of study procedure.

Exclusion Criteria:

1. Those with gastrointestinal symptoms indicative of GERD, gastric carcinoma, previous or current peptic ulcer disease.
2. Those with a history of upper GI surgery prior to this.
3. Those with haematological disorders, bleeding tendency, recurrent nose bleeds or treatment with anti-coagulants).
4. Those who had any previous history of allergy or known intolerance to any of the study drugs or the following formulation constituents: Gaviscon® liquid: sodium alginate, sodium bicarbonate and calcium carbonate
5. Those with physical, neurological or psychiatric conditions preventing repeated visits to hospital or compliance with study procedures.

No masking