Two of the major sources of calories in the American diet are starch and sugar. Starches in the form of bread, pizza and pasta rank second, fifth and seventh on the list of the top 10 ways that Americans consume calories, according to registered dietitian Suzanne Boos. Sugars in the form of grain-based desserts and soda rank first and fourth. By cutting out sugar and starch for two weeks you can lose weight, even if you don't cut your calories.
To lose fat, you need a calorie deficit, where you're consuming fewer calories than you're burning. A calorie deficit of 3,500 will lead to 1 pound of fat loss. Therefore, the amount of fat you can lose by cutting out sugar and starches depends on how much of them you're eating. If you're currently consuming 500 calories per day from starch and sugar, cutting them out would equal 3,500 calories fewer every week, which would lead to 1 pound of fat loss.
The Rapid Loss
People embarking on a low-carb, or a starch- and sugar-free diet often experience initial rapid weight loss, even without cutting calories too much. The Sports Dietitians Australia website notes that this loss is due to a depletion in glycogen -- the stored carbohydrate within the body -- which also causes your body to lose water. This can lead to between a 1 and 3 kilogram, or 2.2 to 6.6 pound loss in just a few days. Once you stop a sugar- and starch-free diet and start eating more carbs, this weight will go back on, though.
Factoring in Fat
When starting a lower-carb diet, you often have to cut out several food groups. If you currently rely on foods like rice, bread, pasta, fruit and cereals for a large proportion of your daily calories, you can end up feeling extremely hungry, leading you to eat more of other types of food. If you eat too much fat on a sugar and starch-free diet, you may not lose any weight, as you're simply consuming too many calories, notes Dr. Michael Eades.
Crunching the Numbers
The amount of weight you can expect to lose when cutting out starch and sugar depends on a number of factors. If your diet is currently heavily based around sugary and starchy foods and you switch to eating mainly lean proteins and green vegetables, you can expect to lose up to 5 or 6 pounds from water weight, plus another 3 to 4 from fat loss. If you already eat a relatively low-carb diet, cut starches and sugars but increase your consumption of fat and protein, you may not lose any weight, or could even gain weight.