The General Motors Diet, often called the GM Diet, is a highly restrictive, seven-day eating plan popularized for its promise of rapid weight loss. This regimen claims to help individuals shed up to 15 pounds (6.8 kg) within a single week by focusing on specific food groups each day. Although widely known by its corporate name, the story that the diet was developed by General Motors for its employees is considered a persistent urban myth with no verifiable evidence. The program is structured as a short-term solution that cycles through different food types.
The Specific 7-Day Meal Plan
The GM Diet enforces a rigid structure that dictates the exact food types permitted for each of the seven days. Day one focuses entirely on fruits, recommending all types except bananas, often emphasizing high-water content melons. Day two switches to only vegetables, which can be eaten raw or cooked, though one baked potato is commonly allowed for breakfast for complex carbohydrates. Day three combines the intake from the first two days, allowing a mixture of fruits and vegetables while still prohibiting both bananas and potatoes.
The midpoint, day four, permits only bananas and milk, typically restricting consumption to approximately eight bananas and three glasses of low-fat milk. Day five shifts focus to protein, including two 10-ounce portions of lean protein (such as beef, fish, or chicken) paired with up to six whole tomatoes. Vegetarians often substitute the meat with brown rice or cottage cheese.
Day six continues the pattern of lean protein, allowing the same portions of meat or a vegetarian alternative, but replaces the tomatoes with an unlimited amount of other vegetables. The final day, day seven, reintroduces complex carbohydrates by allowing brown rice, along with vegetables and unsweetened fruit juice. Throughout the week, followers must maintain high hydration by drinking at least 8 to 12 glasses of water daily. Many variations also encourage consuming an optional “GM Wonder Soup,” a broth-based mixture of cabbage, celery, and other vegetables, whenever hunger strikes.
Mechanism of Rapid Weight Loss
The immediate and substantial weight loss reported by followers stems directly from the diet’s severely hypocaloric and restrictive structure. By focusing almost exclusively on low-calorie, high-fiber fruits and vegetables, the diet creates a significant energy deficit. This drastic reduction in caloric intake forces the body to utilize its stored energy reserves quickly.
A large portion of the weight drop observed in the first few days is due to the loss of water and stored glycogen. Glycogen, the body’s primary carbohydrate store, binds to a significant amount of water; when these stores are depleted due to carbohydrate restriction, the associated water is flushed out. The diet’s emphasis on high-water-content foods and large volumes of water contributes to a powerful diuretic effect. Proponents sometimes claim the foods are “negative-calorie” items that require more energy to digest than they contain, but this concept is not supported by scientific evidence.
Nutritional Completeness and Sustainability
The GM Diet is considered nutritionally unbalanced because its rigid daily structure often restricts or excludes entire macronutrient groups. Certain days, such as the initial fruit and vegetable days, contain very little protein and healthy fats. These fats are necessary for the absorption of fat-soluble vitamins and for overall physiological function.
The lack of consistent, balanced protein intake is a major concern, as the body may break down muscle tissue to meet its essential protein needs. Losing metabolically active muscle mass negatively affects the resting metabolic rate, making long-term weight maintenance difficult. Due to its restrictive nature and lack of diverse nutrient sources, the diet is not intended for long-term use and can lead to temporary deficiencies in vitamins and minerals like calcium and iron.
The rapid weight loss achieved is frequently temporary because the plan is unsustainable as a permanent eating pattern. Since the diet does not educate individuals on balanced eating habits or portion control, weight regain is highly likely once the seven-day period is over. This rebound effect makes the GM Diet a poor strategy for permanent weight management.