Yes, the scale will move, and most of what moves in seven days is water, glycogen and gut contents rather than fat. It is a very low calorie week with no published trial behind it, and nothing in the plan changes the habits that decide whether the weight stays off afterwards.
What is the 7 day GM diet?
The GM diet, also called the General Motors diet, is a seven day sequence in which each day allows a narrow set of foods. Day one is fruit. Day two is vegetables. Day three is both. Day four is bananas and milk. Days five and six add a protein portion. Day seven brings back a grain and some juice. A cabbage based vegetable soup, usually called wonder soup, runs through the whole week, and sugar, wheat, alcohol and added fat are out from start to finish.
The name attaches the plan to a car manufacturer and an employee wellness programme in the 1980s. That story has never been substantiated, no author has ever been identified, and there is no published clinical trial of the seven day sequence. What circulates is a forwarded chart, not a protocol anyone has tested.
That matters less than it sounds, because the mechanism is not mysterious. Take out grains, fat, salt and most of the protein for a week and what is left is a very low calorie diet wearing a timetable.
| Day | What the plan allows | What that day takes out |
|---|---|---|
| 1 | Fruit, usually excluding bananas | Grains, protein, fat, salt |
| 2 | Vegetables, raw or boiled, potato early in the day | Fruit, protein, fat |
| 3 | Fruit and vegetables, no banana or potato | Starch, protein, fat |
| 4 | Bananas, milk and the soup | Almost all variety |
| 5 | A protein portion with tomatoes | Vegetables in any quantity |
| 6 | Protein with vegetables | Carbohydrate |
| 7 | Rice, fruit, vegetables and juice | Fat and most protein |
Can you actually lose weight on it?
Almost everyone who follows the week sees a lower number on day eight than on day one. That is not in dispute, and it is not evidence of much. Any week in which you eat far less than usual, cut salt hard, empty your carbohydrate stores and drink more water will produce the same drop, whatever schedule you dress it up in.
So the useful question is not whether the number falls. It is what the number is made of, and how much of it is still gone a month later.
What is the scale drop actually made of?
Four things move at once during a week like this, and only one of them is fat.
Glycogen and the water held with it. Carbohydrate is stored in muscle and the liver as glycogen, and glycogen is stored wet: each gram of it is held alongside roughly three grams of water. Empty those stores across several very low carbohydrate days and the water leaves with them. Kreitzman and colleagues described this in the American Journal of Clinical Nutrition as an illusion of easy weight loss followed by an apparently excessive regain, because the water comes straight back the moment carbohydrate does.
Sodium and fluid. Cutting salt sharply reduces the fluid your body holds on to. It is real on the scale, close to invisible in the mirror, and reversed by a few normal meals.
Gut contents. You are eating a fraction of your usual volume of food, so there is simply less of it inside you at any given moment.
Fat. A genuine calorie deficit for seven days does produce genuine fat loss. It is the smallest of the four numbers, and it is the only one worth having.
Why does most of it come back?
Because most of what left was never fat. Refill glycogen, eat salt again, and the water returns within days of eating normally. That is not a collapse of willpower and it is not your metabolism punishing you. It is the same physiology that produced the drop, running in the other direction.
The British Dietetic Association puts it plainly in its fad diets fact sheet: rapid weight loss may involve the loss of lean muscle and fluid rather than body fat, and it treats any plan promising more than 1kg of body fat a week as a warning sign in itself. NHS guidance on losing weight points the same way, suggesting a target of 0.5 to 1kg a week and advising against trying to lose weight suddenly with diets. That page carried a 17 March 2023 review date, with its March 2026 review overdue, when it was re-read on 11 October 2026, so treat it as standing advice rather than fresh.
What does the week cost you?
Protein is the main cost. Four of the seven days supply very little of it, and protein is what protects muscle while you are eating less than you burn. Muscle lost during a crash week does not come back on its own when you start eating again, and losing it makes the next attempt harder rather than easier. How much protein does that job, and what the trials actually measured, is in what the trials found on high protein diets for weight loss.
Energy is the second. Eating this little makes training harder and often makes ordinary days harder too. Headaches, feeling light on your feet when you stand up, irritability and poor concentration are common on weeks this restrictive.
The detox framing is the third, and it does not hold up. The liver and the kidneys clear metabolic waste continuously, and they do not need a schedule of fruit days to do it. The BDA covers the claim in its detox diets fact sheet. Feeling lighter after a week of low volume, low salt eating is a real sensation, and it is not evidence that anything was flushed out of you.
The fourth is the hardest to measure and often does the most damage. A week of rigid rules followed by a rebound tends to teach people that they failed, when what actually happened is that the plan had no design for the day after it ended.
Who should stay away from it entirely?
Some people should not attempt a very low calorie week at all, and that is worth settling before rather than after. Speak to a doctor or a registered dietitian first if any of these apply to you:
- pregnancy, breastfeeding, or trying to conceive
- diabetes, especially on insulin or other glucose lowering medication
- any history of disordered eating, or a difficult relationship with food
- a thyroid condition, anaemia, or low blood pressure
- kidney or liver conditions
- regular medication that has to be taken with food, or that needs steady intake to work
- adolescence, or older age where muscle is already being lost
That list is a reason to get advice about your own situation, not a verdict on it. A doctor can tell you in one conversation what an article cannot.
So what actually decides whether fat comes off and stays off?
| The seven day week | A deficit you can actually hold | |
|---|---|---|
| Speed on the scale | Fast in the first few days | Slow, and uneven week to week |
| What comes off | Mostly water, glycogen and gut contents | Mostly fat, when protein and training are in place |
| Protein | Very low on most days | High enough to protect muscle |
| Muscle | At risk | Largely protected |
| Energy for training | Poor | Workable |
| Hunger afterwards | Sharp rebound is common | Manageable, because the gap is smaller |
| Plan for the day after | None | There is no day after, it is the same approach |
| Evidence behind it | No published trial of the sequence | Consistent with mainstream guidance |
The row that decides the outcome is the second from last. A seven day sequence ends on day seven and says nothing about day eight, which is the day that determines everything. A moderate deficit you can hold, enough protein, some resistance training, decent sleep and more walking is slower and far less dramatic, and it is the thing still working in six months. What a calorie deficit actually is covers the arithmetic, and losing weight naturally and keeping it off covers the part that comes after the loss.
If you are going to try it anyway, what makes the week less risky?
None of this makes a crash week a good idea, and if it is happening regardless, some versions of it are safer than others.
- Do it once. Not as a monthly reset, and not back to back.
- Keep fluid intake up, and treat dizziness, palpitations or fainting as a reason to stop and get medical help rather than a sign it is working.
- Keep training light. Walking and stretching, not a heavy programme you are too underfed to recover from.
- Eat the protein on the days that allow it instead of cutting further.
- Plan day eight before you start day one. Reintroducing normal food gradually, with protein and vegetables leading, works better than going straight back to what you were eating before.
- If the weight returns, do not repeat the week. It returned because of what it was made of, and repeating it produces the same result again.
The honest summary is that the GM diet is a way to make the scale move quickly and it is not a way to lose fat. If a fast, visible change before a fixed date is genuinely the goal, it will do that. If the goal is to weigh less next year than this year, the week does nothing towards it and can set you back by costing you muscle.
What has changed since this was first published?
A forwarded chart with no author does not get updates, so the plan itself has not moved. The guidance around it is rechecked on the weekly refresh, and the entries below carry the date and the source.
- 11 October 2026: the NHS weight loss tips page re-read. It still says to aim for 0.5 to 1 kg a week and not to lose weight suddenly with diets, and it still shows a 17 March 2023 review date with its March 2026 review overdue, so the advice is standing rather than fresh.
- 11 October 2026: the two British Dietetic Association fact sheets and the Kreitzman paper were checked and are live. Their wording was not re-read on this pass. No figure on this page has changed.
Frequently asked questions
Does the 7 day GM diet actually work?
It works at making the scale read lower after seven days, which is not the same thing as fat loss. There is no published trial of the sequence, and the drop it produces is mostly water, glycogen and gut contents rather than body fat.
How much of the loss is real fat?
A small fraction of it. Seven days of eating far less than you burn does produce genuine fat loss, and it is dwarfed on the scale by the water released as glycogen stores empty and as salt intake falls.
Will the weight come back after the GM diet?
The water almost always does, within days of eating normally again, because refilling glycogen and eating salt again restores the fluid that left. What happens to the rest depends entirely on what you eat from day eight onwards.
Is the GM diet safe?
For a healthy adult doing it once, the usual complaints are fatigue, headaches and feeling faint. It is not appropriate during pregnancy or breastfeeding, with diabetes, with a history of disordered eating, or alongside several common conditions and medications. Check with a doctor about your own situation first.
Can you repeat the GM diet every month?
Repeating it is the pattern most worth avoiding. Each round risks muscle rather than fat, and cycling between severe restriction and rebound tends to leave people heavier and more discouraged than steady eating would have.
What should you eat after day seven?
Reintroduce food gradually rather than all at once, leading with protein and vegetables and adding grains and fats back over several days. Expect the scale to rise as glycogen and fluid return, and treat that as physiology rather than failure.
Keep reading
- The Dukan Diet: Should You Try It?
- What Is the Korean Switch-On Diet, and Does It Work?
- The Egg Fast Diet: What It Is and What It Actually Does
This article is general information, not medical advice, and is not a substitute for care from a qualified healthcare professional. Speak to your doctor about your own situation.
Leave a Reply