Low Calorie Diets


Examples:  Weight Watchers®, Jenny Craig®, Slim-Fast®.   The idea behind these diets is to eat fewer calories than the body needs, so that excess body fat will be burned for energy.  Learn how calorie reduction affects your metabolism and whether it will suit your chemistry.      

STRATEGY: Eat fewer calories than your body needs.

FOODS: All kinds of food.


All kinds of foods are allowed (psychologically reassuring; people feel less deprived).
Diet works for many people.
Plans are easy to understand.
Plans are structured—this takes a lot of the guesswork out of dieting.
Weight Watchers® and Jenny Craig offer personal support.
Jenny Craig and Slim-Fast® provide prepared meals/snacks, which are convenient.


These diets can work for weight loss but they tend not to improve general health (cholesterol profiles, blood sugar control, etc.) as much as other plans, since all kinds of foods, including some very unhealthy foods, are allowed on a daily basis.

Because fat is high in calories, these diets usually encourage low-fat eating, which:

a) is not necessary for weight loss
b) increases chance of hunger
c) encourages people to eat higher amounts of carbohydrate

These diets allow refined carbohydrates, such as sugar and flour, which may lead to the following issues, especially in carbohydrate-sensitive people:

  • Hunger
  • Fatigue
  • Cold
  • Difficult losing belly weight
  • Weight loss plateaus
  • Anxiety/irritability

Because the diet allows refined carbohydrates, insulin levels can be both too high and too unstable in many people for the body to be able to efficiently, steadily, and comfortably burn fat. Insulin puts the body into sugar-burning, fat-storing mode. In between meals, the body’s blood sugar (glucose) can fall; this is perceived by the body as an emergency, so it will do everything in its power to keep blood sugar even.

First your brain will respond by sending you strong carbohydrate craving signals, hoping you will simply eat some more carbohydrate. If you are somehow able to resist this urge, your body will turn to the liver, where some carbohydrate is stored as glycogen (animal starch). How much can the liver hold? It varies, but somewhere between 250 and 400 calories’ worth. So, depending on what you are doing, you could burn through all of that before your next meal [the body also stores glycogen in muscles, but that glycogen is reserved especially for the muscles to use while exercising]. So, what will your body do to make blood sugar after your liver glycogen supply is gone?

Since the body has a hard time making glucose out of body fat, the body would have no choice but to start breaking down some muscle protein to make some more glucose. This means that some muscle mass may be lost.  As a result, some of the weight lost using this strategy may be muscle instead of fat.


If you choose this kind of weight loss plan, it may be harder on your body and your spirit than most other plans, especially if you are carbohydrate-sensitive. However, there are many individuals who have been very successful using this strategy. I would never want to discourage you from working towards your weight loss goals in any reasonable way that works for you and your lifestyle. If you lose weight with a low-calorie plan, you will still have achieved something very important., because progressing towards a healthier weight reduces your risk for chronic diseases and improves your self-image.

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Last Modified: Sep 3, 2015