Meal replacements should be used in tandem with a healthy lifestyle and professional guidance.

Losing weight is not always easy. Some people who want to shed excess kilos quickly have turned to meal replacement products.

Available in the form of shakes, bars or soups, meal replacements are formulated to replace a complete meal but with lower total calorie content. At just 200 to 250 calories on average per serving, meal replacements do work. However, they should not replace meals totally in the quest for a healthier body weight.

“It is important to learn to incorporate healthy behaviours while aiming for weight loss to achieve sustainable results. A meal replacement may help individuals get a head start on the scale, but it is important to work towards building up long-term healthy eating habits,” said Ms Tan Ai Shan, Principal Dietitian (Clinical), Dietetics Department, Singapore General Hospital (SGH).

“The road to successful weight loss or maintenance is through making positive lifestyle changes and staying consistent with those changes. Working with a dietitian can help individuals find the best long-term eating plan.”

Low-calorie meal replacements are generally not for children, pregnant or breastfeeding women, and those with severe diseases affecting the liver, kidney or heart. Those with pre-existing medical conditions should check with a doctor or dietitian to assess if a diet, particularly a very low-calorie one, is suitable, and how it can be carried out safely and effectively.

For instance, people with diabetes who are taking insulin or oral glucose-lowering medications may need to have their medication adjusted. Low-calorie diets can increase the risk of hypoglycaemia, or low blood sugar.

“When incorporated as part of a caloric-restricted healthy eating plan, meal replacement products can be a useful weight loss tool,” said Ms Tan.

However, some may use them incorrectly — using meal replacements in place of all meals may not provide enough calories, essential nutrients or fibre; while using them in addition to regular meals can lead to weight gain. Some may not be able to tolerate the lactose or sugar alcohols in the products, which can cause bloating, cramps and diarrhoea.

Taking only replacement products is akin to following a very-low-calorie diet (VLCD). Also known as a semi-starvation or crash diet, a VLCD is a clinically supervised diet plan that provides about 800 calories a day. They are usually used for the extremely obese going for bariatric surgery, or those who need to lose weight very quickly to improve certain medical conditions.

Men need on average 2,200 calories a day, while women need 1,800 calories. This means that a VLCD provides far fewer calories than required by most people to achieve a stable and healthy weight. Following a VLCD, said Ms Tan, requires close medical supervision due to the risk of dehydration, electrolyte abnormalities, and gallstone formation.

Meal replacements generally produce significant and sustainable moderate weight loss over a period of six months. VLCDs, for instance, have been shown to be effective in weight management, with an average weight loss of 1.5 to 2.5kg per week.

“Nevertheless, it is important to note that a VLCD is a short-term solution for weight loss, meant to be followed for a limited time only (up to 12 weeks). Individuals will then need to transition to a maintenance plan that includes healthy eating, exercise, and other lifestyle changes,” stressed Ms Tan, adding that such diets can also “take the fun and pleasure out of eating for some people”.

When the body goes on an excessively low-calorie diet for some time, it can experience what is known as the yo-yo diet syndrome. When consuming significantly fewer calories, the body starts to regulate the rate at which it burns calories to support the various daily functions.

That slower rate of metabolism remains even when the person returns to normal eating, which can ultimately lead to weight gain. The yo-yo effect occurs because crash dieting prompts the body to store fat at a faster rate once a person starts eating normally. This is the body’s defensive instinct of trying to store reserves for future periods of deprivation.

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