I focus on clean healthy eating within a calorie deficit. So work out your tdee, there is plenty of calculators on line, then under eat by what you wish to lose, 500 cals under a day averages a pound a week. 1000 under a day is 2 lbs.
so I eat, lean proteins, meat, fish, seafood, and veg and salads, I don’t add fats. I also like fruit, and personally enjoy Huel black as it has 35 g of protein,
it’s important to ensure you eat enough protein when losing, aim for 1g per 1kg of body weight. And exercise, weight and resistance is important, both protein and strength exercises are key so you don’t loose muscle.
losing muscle will simply ensure you regain fast when you stop , muscle helps us burn fat, and it is critical for stability as we get older.
also ensure you drink enough water, some for min of 2litres a day.
i think a lot of folks who have gastro side effects it is down to what they eat. Not all, but a lot. So avoid anything sugary, too many carbs, or fatty foods.
good luck , it’s life changing.