A study by Barbara Rolls of Pennsylvania State University, published in "The American Journal of Clinical Nutrition" in 1999, showed that eating soup before a meal decreased the amount of calories lean women consumed at a meal. Rolls went on to demonstrate that the type of soup eaten before the meal didn't matter much -- subjects who ate soup before a meal generally ate less at the meal than a non-soup control group.
Although research seems to indicate that soup can be an effective part of a weight loss plan, there is no research that conclusively demonstrates how much weight you can lose if you only eat soup for two weeks. Most likely, your results will depend on how much soup you eat and how calorie-rich it is.
It takes an energy deficit of 3,500 calories to lose 1 lb. Cutting back 500 calories per day leads to a weight loss of 1 lb. in about a week, which is about the fastest weight loss that the American Dietetic Association recommends. The number of calories you can cut from your diet by eating only soup depends on what you eat now and the types of soup you start to eat. The United States Department of Agriculture recommends an active adult woman should eat about 2,200 calories per day to maintain weight. Dropping below this intake level should result in weight loss.
The huge array of soup makes it impossible to generalize calorie counts. You could make squash, chickpea and red lentil stew, from "Eating Well" offers filling fiber and protein with 300 calories per serving. If you ate one serving of a similar dish three times a day, your calorie total for the day would add up to 900. If you normally eat about 2,500 calories per day, it would only take you four to five days to lose 1 lb. However, if you opted for a creamy clam chowder at 450 calories per serving, the loss would take longer. Another challenge is avoiding bread and crackers along with your soup.
The diversity of soup makes it possible to eat a wide range of vegetables and legumes while dieting. You can also vary the flavoring style to keep the soup interesting. The warmth of soup could make you feel full on less food, at least for a while.
No matter how flavorful you make soup, or how many different kinds of broth you use, it’s going to get boring after a while. This will make it very tempting to binge on convenient unhealthy foods like French fries or cake, especially if you go out with friends. Even if your soup is made of healthful ingredients, you can still eat too much of it and end up gaining weight. Although you may see an initial weight loss when you first change your diet, the American Dietetic Association says very fast weight loss is usually due to water, bone and muscle loss. When you go back to eating your regular diet, you could gain back everything you lost plus a few bonus pounds.
Canned soups are convenient and they offer the benefit of nutrition information right on the label, so you know exactly how many calories you are consuming. However, most canned products also contain a lot of salt. Look for lower sodium soups. Another problem with any crash diet is that consuming such a limited range of foods also limits the nutrients you can get from food. Consuming one type of soup for two weeks would leave some big gaps in your nutritional profile.