Lose four kg in a couple of days: and keep it off a year later

If you eat extremely little food for a couple of days and do lots of exercise and you’re overweight, you can lose 4-5 kg. And yes: the positive effect on your body composition will still be visible after a year. Spanish sports scientists write about this in the Scandinavian Journal of Medicine and Science in Sports. But before you embark on putting the results of the study into practice, read the whole article not just the abstract. It’ll spare you disappointment.

Losing weight rapidly in a short period of time: competitive athletes do it regularly, but dieticians are against it. If you lose weight too fast you’ll lose comparatively more muscle mass they say. And this is exactly what you see in human studies where people lose more than half a kilogram per week.

But these studies are about slimming attempts that last for weeks. Very short periods – of several days – in which you drastically reduce your calorie intake and exercise intensively don’t have such a dramatically negative effect. And the odd Japanese animal studies we are so fond of in this web magazine confirm this. What’s more, the same animal studies have shown that after this kind of crash diet, muscle mass is restored faster than fat mass.

Lose four kg in a couple of days: and keep it off a year later
Researchers at the University of Las Palmas de Gran Canaria got 15 overweight men – average BMI 30 – to lose about 4 kg over a period of a week. During the first four days the men were only allowed to eat 320 kcal per day. At the same time they walked eight hours a day and also trained their arms on an arm-crank-ergometer [see photo above] for 45 minutes. The combination of exercise and diet meant that every day the men expended 5000 kcal more than they consumed.

The researchers divided the men into 2 groups. One group was given their 320 kcal in the form of whey; the other group got it in the form of sugar [Sucrose].

At the end of the four days the men were allowed to eat as much they needed for the rest of the week. They were not allowed to do much exercise.

The researchers examined the men a month afterwards and a year afterwards. They discovered that the fat loss induced by four days of hardly any food and lots of exercise was still present after a year, and that most of the decrease in lean body mass had been restored.


WCR = after 4 days; DIET = after 7 days; POST = after 4 weeks.

We drew a graph ourselves of the number of kg fat lost as a result of the crash diet and separated out the whey and sugar group. The figure shows that a year after the crash diet the amount of fat still lost in the sugar group was negligible.


How does this work? The article does not make this clear. You might expect that the whey group retained more lean body mass, and therefore also burned more kcals. But if you construct a similar graph of kg lean mass lost, you’ll see that this is not the case.


If you’re planning on repeating the Spaniards’ experiment with yourself as the subject, use whey during your crash diet and not sugar. If you do so the results are likely to last longer, even if you don’t know why.

A time-efficient reduction of fat mass in 4 days with exercise and caloric restriction.


To determine whether a fast reduction in fat mass can be achieved in 4 days by combining caloric restriction (CR: 3.2?kcal/kg body weight per day) with exercise (8-h walking?+?45-min arm cranking per day) to induce an energy deficit of ?5000?kcal/day, 15 overweight men underwent five experimental phases: pretest, exercise?+?CR for 4 days (WCR), control diet?+?reduced exercise for 3 days (DIET), and follow-up 4 weeks (POST1) and 1 year later (POST2). During WCR, the diet consisted solely of whey protein (n?=?8) or sucrose (n?=?7) (0.8?g/kg body weight per day). After WCR, DIET, POST1, and POST2, fat mass was reduced by a mean of 2.1, 2.8, 3.8, and 1.9?kg (P?< ?0.05), with two thirds of this loss from the trunk; and lean mass by 2.8, 1.0, 0.5, and 0.4?kg, respectively. After WCR, serum glucose, insulin, homeostatic model assessment, total and low-density lipoprotein cholesterol and triglycerides were reduced, and free fatty acid and cortisol increased. Serum leptin was reduced by 64%, 50%, and 33% following WCR, DIET, and POST1, respectively (P?http://www.ncbi.nlm.nih.gov/pubmed/24602091