Allegedly created by the General Motors Corporation, the GM diet is a seven-day crash-style diet that involves severe calorie and food restriction, promising a loss of 10 to 17 pounds on average.
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If that sounds too good to be true, there's a reason. The GM diet has no solid research to promote its claims and is likely to cause more health problems than it solves. Before you become convinced by the diet's lofty claims, consider some of the negative side effects you may experience.
Read more: Why You Probably Shouldn't Try the OMAD Diet
What Is the GM Diet?
While the GM diet has inexplicably been attributed to the General Motors Corporation for its formulation, there's no evidence that the company was actually the source of the diet. As a whole, the GM diet is something of an urban legend with no official source or research.
The regimen promises as much as 10 to 17 pounds of weight loss in as little as one week, according to one popular GM diet website. The diet lays out a restrictive seven-day eating plan, allowing only specific food groups on certain days, with little to no research backing the regimen, according to Bonnie Taub-Dix, RD, registered dietitian and author of Read It Before You Eat It: Taking You From Label to Table.
A key part of the diet is hydration, according to the GM site. The plan encourages drinking at least six to eight glasses of water daily and increasing your total water intake each day. Increased hydration, combined with the foods consumed, is said to help improve symptoms of digestive unrest; however, no solid evidence backs up these results.
The GM Diet Plan
- Day 1: Fruit — All fruit (except banana) is allowed on this day with no specific limitations. No other foods can be eaten on this day.
- Day 2: Vegetables — The second day allows all forms of vegetables and recommends that you start the day with a small baked potato.
- Day 3: Fruits and Vegetables — On day three, you can eat all the fruits and vegetables allowed on the first two days. Avoid bananas and potatoes.
- Day 4: Bananas and Milk — This day allows only bananas (up to eight) and milk (up to three glasses of skim milk). You can also include something called "wonder soup," which is a cabbage-based stew.
- Day 5: Meat and Tomatoes — The fifth day allows up to 20 ounces of beef, chicken or fish split into two meals, paired with up to six tomatoes. For those that are vegetarian, the meat can be replaced with cottage cheese and brown rice.
- Day 6: Beef and Vegetables — Similar to the previous day, you can consume up to 20 ounces of beef this day with unlimited vegetables (no tomatoes or potatoes).
- Day 7: Brown Rice, Vegetables and Fruit Juice — This day allows unlimited amounts of brown rice, vegetables and fruit juice.
Why You Should Skip the GM Diet
Just like every crash diet or weight-loss fad has its drawbacks, there's little benefit to gain in trying the GM diet, according to Taub-Dix.
"When you think about a diet, you think about something that could actually sustain you and not be something that is temporary," she says. "I don't know how much more information needs to be out there on diets that don't work, where all the people lose a lot of weight and gain it all back, and then some — but this is one of those diets."
1. It's Unsustainable and Any Weight Loss Is Temporary
It shouldn't be too shocking to learn that the GM diet is a highly unsustainable regimen. The plan creates an extreme calorie deficit (when you burn more calories than you consume), which can cause symptoms like fatigue and lightheadedness, according to Taub-Dix. This is why the diet actually advises against exercise, especially in the first few days.
An extreme calorie deficit can also be hazardous to your health, potentially slowing your metabolism, burning your muscle mass and decreasing your bone density. Calorie-restricted eating will also cause you to feel hungrier and can affect your hormone levels.
Not only can the extreme deficit cause unfavorable symptoms, but it will likely cause you to re-gain the weight and perhaps even add more, says Taub-Dix. You can't maintain an extreme deficit for long, and when you begin to eat normally again, you're likely to regain any weight you lost.
2. It Can Lead to Nutritional Deficiencies
Eating a variety of foods is crucial for your health and can help ensure your body is getting all the macro and micronutrients it needs, according to the Office of Disease Prevention and Health Promotion's 2015-2020 Dietary Guidelines for Americans.
Consuming only one type of food will lead to an imbalance of protein, carbohydrates and fats. Eating a balance of the three macronutrients helps promote satiety and gives you the energy you need for the whole day, according to Taub-Dix. Eating only vegetables or only fruit leaves you lacking protein and fat, whereas eating only beef and vegetables will likely leave you deficient in carbs.
At the micronutrient level (vitamins and minerals), eating a variety of foods is necessary to fuel your body properly, as no single food group can supply all the nutrients you need in the amounts your body requires to function, according to the ODPHP.
For example, while cheese will supply your body with plenty of vitamin B12, it lacks sufficient vitamin C. On the other hand, an orange will give you plenty of vitamin C but not enough B12.
Nutrient deficiencies can lead to numerous negative side effects, including fatigue, mental fog, hair loss, irregular heartbeat and vision deterioration, according to Rush University Medical Center. While these side effects aren't necessarily guaranteed (different people will experience different symptoms), it's better to skip the diet altogether to stay on the safe side.
If you do experience any of these symptoms, it's best to consult your health care provider to properly diagnose or target which nutrient you may be lacking. Taking regular blood tests can also help you regulate any deficiencies you may be experiencing.
3. It Can Disrupt Your Digestive System
Let's be honest: A full day of milk and bananas is a recipe for digestive unrest, Taub-Dix says.
Not to mention, consuming solely vegetables and fruit may overload your body with fiber, too, a nutrient that (while healthy) slows the rate at which food is digested in your system. Especially for individuals with intestinal disorders, eating too much fiber can increase bloating or gas production, according to the International Foundation for Gastrointestinal Disorders.
GM Diet Takeaways
While there's little that you stand to gain by following the GM diet, the plan's emphasis on incorporating fruits and vegetables is one positive aspect, Taub-Dix says. Although you certainly shouldn't consume only these food groups, incorporating more fruits and vegetables is a great way to add more nutrition to your meals without adding many calories.
For some people, limiting fat intake (but not as extreme of a limitation as the GM diet promotes in the first two days) can also promote weight loss, if that's your goal, Taub-Dix says.
Nevertheless, the diet as a whole is an unsustainable, unhealthy plan, says Taub-Dix. If the potential nutritional deficiencies, the digestive unrest or the diet's unsustainable structure don't have you convinced against it, consider her final words of advice:
"If you're thinking of going on this GM diet, don't."
- GM Diet: "The GM Diet Plan: Lose Your Excess Weight in Just 7 Days – GMDiet"
- Office of Disease Prevention and Health Promotion: "Key Recommendations: Components of Healthy Eating Patterns - 2015-2020 Dietary Guidelines"
- Rush University Medical Center: "6 Signs of Nutrient Deficiency"
- International Foundation for Gastrointestinal Disorders: "Dietary Fiber"