Water is the medium in which most cellular activities take place, including the transporting and burning of fat. In addition, drinking plenty of calorie-free water makes you feel full and eat less. Drink at least 1oz of water per 2lbs of bodyweight a day (that's 100oz for a 200-lb person). Keep a 20-oz water bottle at your desk, fill it five times a day, and you're set.
Listen to your mum - dieting is faddish. Instead, improve the "quite" to "all" healthy and eat only nutritionally balanced, healthy foods. Cut out all sweets and junk foods, apart from an occasional treat, as humans would have always done till recent times. The exercise is important, and include plenty of stealth exercise, such as taking the stairs instead of the elevator and cycling to the shops instead of driving, etc.
It’s called a “beer belly” for a reason. Boozy bubbles are a major cause of belly bloat, as anyone who’s ever looked in the mirror after a few too many drinks can attest. But it’s not just the carbonation that is the culprit. Alcohol can lead to an overgrowth of bad bacteria in your stomach, leading to gas, not to mention all the empty calories that are going straight to your waistline. Instead, skip the alcohol altogether or limit yourself to one serving per day.