What research says about keto, the egg diet and the units diet

Keto, the egg diet and the units diet each promise something different. Here we look at what the trials show, where there are any.

Keto and low-carbohydrate diets

Keto cuts carbohydrates sharply, usually to under 50 g a day. ‘Low-carbohydrate’ diets are milder. This is what the large comparisons with low-fat diets found:

It is fairly certain that keto gives at most a small extra weight loss and raises LDL on average. The analyses give averages. If you follow keto, it is worth having your cholesterol checked with your doctor.

Insulin. It is often said that keto makes you lose weight because it lowers insulin. In one study, 20 adults stayed in a clinic and ate as much as they wanted, two weeks on keto and two on a low-fat plant-based diet. On the second diet they ate 689 kcal a day less. The study was small and short, but it does not fit the idea that insulin is the key.

The first week's kilos. At the start of keto the scales drop fast, mainly because of water that leaves along with glycogen. See the article on the rate of weight loss.

Side effects. In a 24-week trial of 120 adults:

The trial was funded by the Robert C. Atkins Foundation, and only the keto group received supplements. So it is of low certainty. In this trial keto led to more weight loss.

What the guidelines say. The 2013 US guideline found no difference at 6 months between a low-carbohydrate and a low-fat diet. NICE (2025) says the deficit can be achieved in whatever way suits the person. It advises avoiding strict diets that are not balanced, because they do not work in the long term and may cause harm.

The MesogeaFit app has a ‘fewer carbohydrates’ option, with at least 40% of calories from carbohydrates, but no keto plan.

The boiled egg diet

Diets that go by this name have you eat mostly boiled eggs and a few other foods for one or two weeks. In October 2026 we searched two large databases of scientific studies and found no trial that tests it.

There are studies of eggs as part of an ordinary diet with fewer calories:

• 152 adults, 8 weeks: two eggs for breakfast, five days a week, together with a 1,000 kcal deficit, gave −2.6 kg against −1.6 kg with a bagel breakfast of the same calories. Without a deficit, the eggs made no difference. The study was funded by the US egg industry body.
• 110 adults, 6 months: eggs or cereal for breakfast, with fewer calories, gave 8.1 and 7.3 kg, with no difference. Funded by the Australian egg industry body.
• 128 adults with prediabetes or type 2 diabetes: with 12 or more eggs a week or with few eggs, weight loss was similar. No adverse changes in cardiometabolic health were seen over 12 months. We did not check who funded this study.

From these studies we conclude that eggs fit into a diet, but the result comes from the calories. A 50 g egg has about 70 kcal and 6 g of protein. A diet built on a single food is exactly the kind of unbalanced diet that NICE advises against. And the kilos that come off quickly in a week like this are largely water, which comes back.

The units diet

We found no official Greek source that defines the ‘units diet’. Systems that go by this name give each food a number of units or points, with a limit for each day. Some versions may count carbohydrate units instead of calories, but we have not confirmed this.

We found no trial comparing units with calorie counting. The trials that exist tested a whole commercial programme, Weight Watchers, known for its points system. In the largest trial, however, the programme is described as a diet with fewer calories, weekly weigh-ins, a discussion group and behavioural advice, with no mention of points.

It is fairly certain that a programme with structure, weekly weigh-ins and support helps a little. Whether the units themselves add anything beyond calorie counting, we don't know. Units look like a simplified way of counting calories.

What they all have in common

In a one-year trial, 160 adults followed four well-known diets: Atkins, Zone, Weight Watchers and Ornish. They lost 2.1 to 3.3 kg, with no real difference between them. How much each person lost was related to how closely they followed their diet, not to which one they chose. An analysis of 48 trials with 7,286 adults concluded that the differences between diets are small, and that it is worth choosing the one you can keep to.

Who needs to be careful

• Keto and very low-carbohydrate diets: if you take SGLT2 inhibitors for diabetes, do not follow keto or a very low-carbohydrate diet. If you take insulin or sulphonylureas, do not try it without your doctor. In the clinic study, one healthy participant withdrew because of hypoglycaemia. Take care also in pregnancy and breastfeeding, with kidney disease, with high LDL or familial hypercholesterolaemia, with an eating disorder now or in the past, and under 18.
• Single-food diets: we do not recommend them for anyone, especially people who have or have had an eating disorder, in pregnancy, under 18 and with an egg allergy.
• Programmes with units: the two large trials reported no problems caused by the programme. The same exceptions apply as for any diet with a calorie deficit.