void UpdateJournal(object sender, EventArgs args)
        {
            var calendar = NSCalendar.CurrentCalendar;

            var startDate = DateTime.Now.Date;
            var endDate   = startDate.AddDays(1);

            var sampleType = HKSampleType.GetQuantityType(HKQuantityTypeIdentifierKey.DietaryEnergyConsumed);
            var predicate  = HKQuery.GetPredicateForSamples((NSDate)startDate, (NSDate)endDate, HKQueryOptions.None);

            var query = new HKSampleQuery(sampleType, predicate, 0, new NSSortDescriptor[0], (resultQuery, results, error) => {
                if (error != null)
                {
                    Console.WriteLine("An error occured fetching the user's tracked food. " +
                                      "In your app, try to handle this gracefully. The error was: {0}.", error.LocalizedDescription);
                    return;
                }

                InvokeOnMainThread(() => {
                    FoodItems.RemoveAllObjects();
                    foreach (HKQuantitySample sample in results)
                    {
                        var foodName  = (NSString)sample.Metadata.Dictionary [HKMetadataKey.FoodType];
                        double joules = sample.Quantity.GetDoubleValue(HKUnit.Joule);
                        var foodItem  = FoodItem.Create(foodName, joules);

                        FoodItems.Add(foodItem);
                    }

                    TableView.ReloadData();
                });
            });

            HealthStore.ExecuteQuery(query);
        }