Rapid weight loss has long been viewed with apprehension. There is often a negative stigma associated with diets that lead to an abrupt loss of weight, as people believe that this results in negative outcomes once they return to alternate patterns of eating.

But, extensive research conducted by various health professionals has suggested otherwise.

Rapid weight loss is often achieved by following a very low-calorie diet (VLCD). This type of diet involves very low daily energy consumption in the form of about 800-1200 calories. They are generally only used for short bouts, as people often say they can be difficult to follow.

In truth, VLCDs are formulated, nutritionally complete meals and can be produced as either a shake or bar, or as dietitian-approved meals to ensure an adequate balance of nutrients is achieved.

While following a VLCD, you will enter a state of Ketosis. Ketosis is a normal metabolic process that occurs when your body doesn’t have enough carbohydrates to burn for energy, so it uses stored fat as an alternative. This is generally achieved when your daily carbohydrate intake is <50g, which is equivalent to three medium potatoes or three slices of bread.

Once a very low calorie/ketogenic diet is commenced, it will usually take the individual three to four days (depending on their physical activity levels) to deplete glycogen stores. Lethargy, fatigue, hunger and headaches are common during this time as the body ‘fat adapts’ to its new preferred and primary source of fuel. During the breakdown of fat, your body produces ketones (a byproduct of fat metabolism) which assists in suppressing your appetite and reducing your hunger hormones (Grehlin), which in turn results in rapid weight loss.

Initially, you can expect to lose 1-3kg of fluid and glycogen, as every gram of carbohydrate within the body holds an extra 3g of fluid. This is regained rapidly once you switch out of ketosis; however, those who do follow a rapid weight loss diet often see between 10-25% weight reduction in the first three to six months. After four years, 5% of weight loss is maintained.

In the short term, rapid weight loss diets have been shown effective by scientific evidence all over the world to fight obesity, hyperlipidaemia (i.e. high levels of fat in the blood), and some cardiovascular risk factors such as high blood pressure. Additional benefits include higher satiety and feelings of fullness due to the higher protein intakes, reductions in fat production and increases in fat breakdown, and increased metabolic costs as the body uses more energy to breakdown fat and protein as an energy source in comparison to carbohydrates.

Ketosis also reduces insulin levels (a fat-storage hormone). Insulin activates enzymes, which store energy derived from carbohydrates. As carbohydrate intakes subside, so does insulin and therefore decreases in fat formation and accumulation are significantly evident. A recent study looked at the effects of a weeklong ketogenic diet on Type 2 diabetes mellitus patients. The results showed significant decreases in blood sugar levels as well as markers of body composition (weight, waist circumference, body fat %).

Interestingly, ketogenic/rapid weight loss diets are also widely used in the treatment of epilepsy, as it has proven effective in controlling seizures and other neurological patterns. Studies show that approximately 35% of children treated with the ketogenic diet have greater than 90% seizure control with half of these becoming seizure-free.

If you’re hesitant about losing weight in a short period of time, consider all the emerging evidence that suggests those who follow a rapid weight loss diet achieve greater weight loss in the short- and long-term, and reduce their susceptibility of regaining the weight.