Forget exercise and low fat , although exesrsise is essential for good health, one would have to run a marathon to lose 3lb
To lose weight you will have to change perhaps a lifetimes habits and THINKING around food and DRINK.
To lose weight you will need to eat less calories than your body needs to maintain it's weight. NEVER less than 1,000 per day.
The best way to succeed is to cut out all refined sugars and refined carbohydrates. The easiest way to do this is to only eat basic foods, that is foods which are unprocessed. As Doctor Hillary Jones said only eat foods that don't have an ingredients label on them. Refined Sugars are things such as; granulated, castor, brown sugar ect. Syrups, anything that ends with OSE such as; dextrose, glucose, maltose, sucrose, fructose, etc. lactose in milk is ok.
This means giving up chocolate, sweets, cakes, deserts, ready meals,biscuits, ALCHOL , soft drinks, smoothies, and more.
Refined charbohydrates are grains that have their husks removed and are finely milled; such as white flour, most breakfast cereals, porridge oats is a very good breakfast, but not cup a porridge or Oats so simple, or Ready Break as they are to processed. Granary bread is ok.
I am 70years old at a healthy weight ,with low blood presure, cholesterol, and sugar levels, a very good BMI and very fit.
I have a bowl of porridge for breakfast, 1slice of granary bread butter and cheese for lunch, or a tin of sardines in olive oil, or 1boiled egg with I slice of granary bread, for lunch and my evening meal consists of a large portion of boiled potatoes lots of vegetables with meat, fish or other unprocessed protein. I try to keep to this with no snacks, or treats. I drink mainly hot or cold water and one cup of decaffeinated coffee made with milk, no sweeteners, or sugars.
You might think you would never be able to stick to this . I used to calorie count it is scientific. if you do it accurately you will lose weight. Now I just follow the above advice and if I gain a pound or two I reduce my portion size.
When you eat , or drink refined charbohydrates they mess up your insulin levels, Sugar Spikes and cause cravings the diet I follow is easier, but I am human and my brain can seduce me into old habits (very rarely now), but years of practice has made me an expert in ME and of all of the edible treats nothing tastes as good as being slim feels.