What is very low calorie diet ?

What is Very Low Calorie Diet

Very low calorie diets (VLCDs) is a special diet that provides up to 800 calories per day (<3350 kJ/day) that have been used since the 1970s to induce rapid weight loss ¹. Very low calorie diets use commercial formulas, usually liquid shakes, soups, or bars, which replace all your regular meals. These formulas are not the same as the meal replacements you can find at grocery stores or pharmacies, which are meant to replace one or two meals a day. This type of diet is used to promote quick weight loss, often as a way to jump-start an obesity treatment program. Very-Low-Calorie Diet formulas are designed to provide all of the nutrients you need while helping you lose weight quickly. However, this type of diet should only be used for a short time—usually about 12 weeks. Very low calorie diets (VLCDs) reached the height of their popularity in the United States in 1988 when Oprah Winfrey announced to her television audience that she had lost 67 pounds by consuming a liquid diet ¹. Interest in this approach declined sharply in 1990 when Winfrey reported that she had regained her lost weight and would “never diet again.” In addition, three recent reviews concluded that VLCDs are associated with greater long-term weight losses than are conventional reducing diets ², ³, ⁴.

An expert panel convened by the National Heart, Lung, and Blood Institute ⁵ defined very low calorie diets as diets providing fewer than 800 kcal/d ⁵, the same definition used by a recent European expert panel ⁶.

However, it’s very important to note that the definition of a very low calorie diet is arbitrary. A 700 kcal/day diet, for example, would induce a relatively modest energy deficit in a short, sedentary woman with an resting energy expenditure of 1100 kcal/d. In contrast, a 1200 kcal/day diet would induce a substantial energy deficit in a tall man with an resting energy expenditure of 2500 kcal/day. The man would seem to have a greater risk of adverse metabolic effects (described later), even though technically he was prescribed an Low Calorie Diet (LCD) and the woman a Very Low Calorie Diet (VLCD). Thus, an alternative definition of a Very Low Calorie Diet (VLCD) is a diet that provides <50% of an individual’s predicted resting energy expenditure ⁷.

The diets are designed to produce rapid weight loss while preserving lean body mass.

This is accomplished by providing large amounts of dietary protein, typically 70 to 100 g/day or 0.8 to 1.5 g protein/kg ideal body weight ⁸, ⁵.

Protein may be obtained from a milk, soy, or egg based powder, which is mixed with water and consumed as a liquid diet. Such diets may provide up to 80 g carbohydrate/d and 15 g fat/day, and they include 100% of the recommended daily allowance for essential vitamins and minerals. Alternatively, protein may be obtained from a protein-sparing modified fast, consisting of servings of lean meat, fish, and fowl ⁹, ¹⁰. The modified fast must be supplemented with a multivitamin and 2 to 3 g/d potassium. Both diets require patients to drink 2 L/d non-caloric fluids ⁸. The two approaches produce comparable short-term weight losses ¹¹. Thus, the choice of diet may be left to patient preference. Some investigators severely restrict carbohydrate to induce ketosis, which is thought to reduce hunger ⁹, ¹⁰, ¹¹. However, comparable hunger ratings have been reported with ketotic and non-ketotic VLCDs ¹². In a comparison of psychological adjustment during the baseline and low-calorie diets, the initial 2 wk of dieting was associated with a decrease in appetite and elevation of psychological well-being, regardless of the composition of the diet. Thereafter, appetite and mood approached basal levels. Further changes in these psychological reactions to dieting did not vary with the type of diet. There was no support for the idea that a minimal-carbohydrate, protein-supplemented fast decreases appetite and elevates mood more in comparison with a similar diet containing enough carbohydrate to minimize ketosis ¹².

Very Low Calorie Diet Results

A literature review of the very low calorie diets from 1966 through 1992 ¹³ showed that weight loss on very low calorie diet averages 1.5 to 2.5 kg/wk; total loss after 12 to 16 weeks averages 20 kg. These results are superior to standard low-calorie diets of 5020 kJ/d (1200 kcal/d), which lead to weight losses of 0.4 to 0.5 kg/wk and an average total loss of only 6 to 8 kg. There is little evidence that intakes of less than 3350 kJ/d (800 kcal/d) result in better weight losses than 3350 kJ. Intake of at least 1 g/kg of ideal body weight per day of protein of high biologic value appears to be important in helping to preserve lean body mass. Serious complications of modern VLCDs are unusual, cholelithiasis (the formation of gallstones) being most common ¹³.

Another review of studies on long-term outcome for dietary treatment of obesity published between 1931 and 1999 ¹⁴ included 17 publications and 21 study groups, comprising 3030 patients. Of these 2131 (70%) were followed-up for 3-14 years (median 5 years). Mean initial weight loss ranged from four to 28 kg (median 11 kg). The median success rate of 15% of followed-up patients fulfilled one of the criteria for success. Overall, success rates seemed stable for up to 14 years of observation. Diet combined with group therapy lead to better long-term success rates than did diet alone or diet combined with behaviour modification. Active follow-up was generally associated with better success rates than was passive follow-up (19% vs. 10%). Conventional diet seemed to be most efficacious in addition with group therapy, whereas Very Low-Calorie Diet apparently was most efficacious if combined with behaviour modification and active follow-up ¹⁴.

A meta-analysis of 29 reports on the long-term (more than 5 years post weight loss intervention program) weight-loss maintenance of individuals completing a structured weight-loss program ¹⁵. Five years after completing structured weight-loss programs, the average individual maintained a weight loss of >3 kg and a reduced weight of >3% of initial body weight. After very low calorie diets or in individuals who lost greater than 20 kg of body weight, individuals maintained significantly more weight loss than after hypoenergetic balanced diets (diets that were designed to provide 600 kcal/day (2,520 kilo joule (kJ)) less than the individually estimated energy requirement) or weight losses of <10 kg. Weight-loss maintenance did not differ significantly between women and men. Six studies reported that groups who exercised more had significantly greater weight-loss maintenance than did those who exercised less ¹⁵.

A multicenter evaluation of a proprietary weight reduction program for the treatment of marked obesity ¹⁶. A total of 517 obese patients (407 women and 110 men) participated in a proprietary program that included 12 weeks of treatment by very-low-calorie diet within a 26-week program of life-style modification. Patients were treated in two cohorts (6 months apart) according to a standardized protocol implemented at 18 hospital-based clinics across the nation. Fifty-six percent of women and 54% of men completed treatment, at which time their weight losses were 22.0 kg and 32.1 kg, respectively. Weight losses of women and men who discontinued treatment averaged 14.3 kg and 20.0 kg, respectively. Weight loss was associated with significant improvements in blood pressure and total serum cholesterol levels. A 1-year follow-up evaluation of 74% of patients in the second cohort who completed treatment revealed that they maintained 15.3 kg of their 24.8 kg end-of-treatment weight loss; 59% of patients maintained a loss of 10 kg or more ¹⁶.

In a small study ¹⁷ involving 40 type 2 diabetes subjects with body mass indexes (BMIs) of 30-40 kg/m2 were randomized to one of two 800-kcal diets for 12 weeks. Group A received liquid supplement only, and group B received supplement plus an evening meal. Both groups received an intensive behavioral education program. Results: weight loss and improvements in glycemic, blood lipid, and blood pressure parameters were similar for the two groups. Weight loss averaged 15.7 kg for the entire group. The need for insulin, anti-diabetes, and anti-hypertensive medication decreased significantly. No serious side effects were observed.
In conclusion, both food-containing and supplement diets providing 800 kcal a day effectively promote weight loss for obese individuals with type 2 diabetes ¹⁷.

The National Task Force on the Prevention and Treatment of Obesity, National Institutes of Health, concluded that the current very low-calorie diets are generally safe when used under proper medical supervision in moderately and severely obese patients (body mass index [weight in kilograms divided by height in meters squared] >30) and are usually effective in promoting significant short-term weight loss, with concomitant improvement in obesity-related conditions. Long-term maintenance of weight lost with very low-calorie diets is not very satisfactory and is no better than with other forms of obesity treatment. Incorporation of behavioral therapy and physical activity in very low-calorie diets treatment programs seems to improve maintenance ¹⁸.

Very Low Calorie Diet and Weight Loss Maintenance

An additional study, published in The New England Journal of Medicine in 2010 ¹⁹, looked at the role of protein and glycemic index upon weight loss maintenance. Researchers first implemented a very low-calorie diet (800 kcal per day with the use of Modifast products (Nutrition et Santé). Participants could also eat up to 400 g of vegetables, providing a total, including the very low-calorie diet, of 800 to 1000 kcal per day) to produce the weight loss, then examined whether protein and glycemic index impacted weight loss maintenance.

The study population was made up of 773 overweight adults from European countries who had lost at least 8% of their initial body weight with a very low-calorie diet. Participants were then assigned one of five diets to prevent weight regain over a 26-week period:

• Low-Protein and Low-Glycemic-Index diet,
• Low-Protein and High-Glycemic-index diet,
• High-Protein and Low-Glycemic-index diet,
• High-Protein and High-glycemic-index diet,
• or a control diet.

The low-protein-high-glycemic-index diet was associated with subsequent significant weight regain, and weight regain was less in the groups assigned to a high-protein diet than in those assigned to a low-protein diet, as well as less in the groups assigned to a low-glycemic-index diet than in those assigned to a high-glycemic-index diet.

These results show that a modest increase in protein content and a modest reduction in the glycemic index led to an improvement in maintenance of weight loss ¹⁹.

Very Low Calorie Diet in Obese Type 2 Diabetes

A small study was conducted with fifty-one obese subjects (24 with diabetes and 27 obese without diabetes) to compare weight loss and change in body composition in obese subjects with and without type 2 diabetes mellitus during a very-low-calorie diet (VLCD) program ²⁰. After 24 weeks of intervention, there was no difference in weight loss between the 2 groups. Both groups completing the study per protocol had near-identical weight change during the program, with similar weight loss at 24 weeks (diabetes: 8.5 ± 1.3 kg vs control: 9.4 ± 1.2 kg). Change in fat mass index correlated with change in body mass index (BMI) in both groups, but change in fat mass index per unit change in BMI was less in the diabetic group compared with controls, which persisted after adjusting for age, sex, and baseline BMI. Insulin concentrations remained higher and peak β-hydroxybutyrate concentrations were lower in the diabetic compared with the control group. The conclusion was while following a 24-week very-low-calorie diet program, obese subjects with and without diabetes achieved comparable weight loss; but the decrease in body fat per unit weight loss was less in diabetic subjects. Hyperinsulinemia may have inhibited lipolysis in the diabetic group; however, further investigation into other factors is needed ²⁰.

Very Low Calorie Diet for Weight Loss

Most evaluations of very low calorie diets have consisted of single-site case series conducted at academic medical centers or in individual physician practices. Most studies found that patients who completed a comprehensive very low calorie diet program (that included lifestyle modification) generally lost 15% to 25% of initial weight in 3 to 4 months ², ³, ²¹, ²², ²³, ²⁴, ²⁵. Attrition in these programs typically ranged from 25% to 50% during the first 3 to 6 months, and patients generally regained 40% to 50% of lost weight 1 to 2 years after treatment, in the absence of follow-up care ²³, ²⁴, ²⁵.

The National Heart, Lung, and Blood Institute expert panel did not recommend the use of very low calorie diets over low calorie diets (LCDs) providing 1000 to 1500 kcal/d of conventional foods ⁵. The panel’s conclusion was based on data from randomized trials that showed no differences in long-term weight losses between very low calorie diets and low calorie diets, principally because of greater weight regain after very low calorie diets ⁵.

Despite this expert panel’s conclusion, the majority of individual randomized trials showed slightly larger long-term weight losses for persons prescribed very low calorie diets. Anderson and colleagues, in a meta-analysis of long-term studies, concluded that very low calorie diets were associated with greater long-term weight reductions than low calorie diets ². The studies included in that review, however, were mostly case series, and the meta-analysis did not account for the possibility of differential attrition among patients consuming either a low calorie diet or a very low calorie diet. Astrup and Rossner ³, in a qualitative review of several studies, also concluded that the larger initial weight losses induced by very low calorie diets were associated with greater long-term weight losses. Their conclusion assumed that patients participated in a weight maintenance intervention that included lifestyle modification. In addition, the European SCOOP-VLCD report noted that long-term weight losses may be greater after larger initial reductions in weight ⁶. Given the conflicting conclusions of these reviews, a new meta-analysis of six randomized controlled trials that compared very low calorie diets (VLCD) and low calorie diets (LCD) that were published between 1989 and 1997 ²⁶, ²⁷, ²⁸, ²⁹, ³⁰, ³¹ were reviewed, to determine whether combining study results would reveal any incremental long-term benefit of very low calorie diets ¹.

The majority of studies enrolled patients with a BMI of 35 to 40 kg/m2. Two studies enrolled only women and two other trials enrolled only patients with type 2 diabetes. Participants were prescribed very low calorie diets for 8 to 24 weeks, and the total length of treatment ranged from 6 to 26 months. Three studies used liquid meal replacements, one used a protein-sparing modified fast and two studies used a combination of the two approaches. In three studies, patients were provided with exercise goals, which consisted of daily walking. For the low calorie diet (LCD) group, all six studies prescribed hypocaloric diets comprised of conventional foods, with energy goals ranging from 1000 to 1800 kcal/d.

Short-Term Weight Loss: Participants in the very low calorie diet and low calorie diet (LCD) arms of the studies lost a mean of 16.1% and 9.7% of initial weight, respectively. The mean difference of 6.4% was highly significant, revealing the short-term superiority of the very low calorie diet regimen, which was prescribed for a mean of 12.7 ± 6.4 weeks.

Long-Term Weight Loss: At follow-up assessment, which ranged from 1 to 5 years after completing the very low calorie diet, mean weight losses in the very low calorie diet and low calorie diet groups were 6.3% and 5.0% of initial weight, respectively. The difference between groups was 1.3 %, which was not statistically significant. Very low calorie diet and low calorie diet patients regained 62% and 41% of lost weight, respectively.

Discussion: This meta-analysis ¹ of six studies showed that very low calorie diets induced significantly greater short-term weight losses than low calorie diets but comparable long-term changes in weight. The equivalence of long-term losses was attributable to greater weight regain among the very low calorie diet-treated patients. The present findings support the conclusion of the National Heart Lung and Blood Institute expert panel ⁵ that very low calorie diets not be recommended in lieu of low calorie diets comprised of conventional foods ⁵. The strength of the present conclusion resides in the examination of studies that directly compared very low calorie diets and low calorie diets, in head-to-head trials, rather than extrapolating across investigations, in which only one or the other diet was used ². Results of this analysis should resolve the conflicting conclusions of prior reviews. The relative absence of adverse events reported in very low calorie diet participants in these six trials (particularly that no patient developed symptomatic cholelithiasis (the formation of gallstones)) may have been attributable to lack of detailed assessment.

Conclusion: Except in highly selected cases, we do not recommend the use of expensive very low calorie diets to induce losses of 15% to 25% of initial weight. Although both weight-loss and dropout rates were more favorable for the VLCD group than for the 1200–1500-kcal/d Low Calorie Diet group and the 1500–1800-kcal/d restricted normal-food group, the present findings indicate that few patients will be able to maintain these losses, even under the best of circumstances. Furthermore, numerous studies have shown that obese individuals who lost 10% to 12% of initial weight, at follow up (for 1 year or more) were also associated with greater weight regain even when provided behavioral weight maintenance therapy ³², ³³, ³⁰, ³⁴, ³⁵, ³⁶ or pharmacotherapy. Weight losses of this size clearly are associated with significant improvements in health and well being ⁵, including a reduction in the risk of developing type 2 diabetes ³⁷, ³⁸.

Further research is needed to determine the optimal macronutrient composition of meal replacements for treating obese persons with different weight-related conditions including type 2 diabetes, hypertension, and hyperlipidemia. Preliminary findings, for example, suggest that high-protein, low-carbohydrate diets may substantially improve glycemic control in obese patients with type 2 diabetes ³⁹ and may be more effective, in this regard, than traditional, low-fat reducing diets ⁴⁰. The first of two studies conducted by Wing et al. ⁴¹ similarly observed superior glycemic control among patients treated with a high-protein VLCD than with a more traditional, low-fat LCD, despite comparable weight losses. However, widespread adoption of the low-carbohydrate approach for diabetic patients should await further long-term safety data concerning lipids, cardiovascular and renal disease, and bone mineral density.

Very Low Calorie Diet Meal Plan

A very low-calorie diet is a special type of diet that replaces all of your meals with prepared formulas, often in the form of liquid shakes ⁴². VLCDs use commercial formulas, usually liquid shakes, soups, or bars, which replace all your regular meals. Others, such as the fad grapefruit diet (also called the Hollywood Diet), rely on eating a lot of the same low-calorie food or foods.

Very low-calorie diets formulas are not the same as the over-the-counter meal replacements you can find at grocery stores or pharmacies, which are meant to replace one or two meals a day.

Very low calorie diet formulas are designed to provide all of the nutrients you need while helping you lose weight quickly. However, this type of diet should only be used for a short time—usually about 12 weeks.

Depending on a number of factors, healthy adults need different amounts of calories to meet their daily energy needs. A standard amount is about 2,000 calories. A very low-calorie diets provide far fewer calories than most people need to maintain a healthy weight. This type of diet is used to promote quick weight loss, often as a way to jump-start an obesity treatment program.

• Very low-calorie diet (VLCD) may be used for a short time to promote quick weight loss among some people who are considered to be obese.
• The diet requires close care from your doctor and is usually combined with other ways to lose weight.
• Do not go on a VLCD on your own. If you need to lose weight, talk to your health care provider about the approaches that may work best for you.

Clinical Use of Very Low Calorie Diets

In the United States, very low calorie diets are generally used as part of a comprehensive intervention that includes medical monitoring and a program of lifestyle modification. Care is provided by a physician, often in conjunction with a dietitian, psychologist, and/or exercise physiologist. Treatment, including the cost of the very low calorie diet, is typically $1800 to $2200 for the first 12 weeks, during the period of rapid weight loss ⁴³. An additional 12 to 14 weeks of refeeding (in which conventional foods are reintroduced) and weight stabilization bring total costs for 6 months to $3000 to $3500 ⁸.

In European Union nations, very low calorie diets are frequently used with less medical supervision than provided in the United States. In most countries, diet products can be purchased over-the-counter or from a pharmacist without a prescription (except in France). As recommended by the SCOOP-VLCD report, prepared by an expert European panel, consumers may use a very low calorie diet as a sole source of nutrition for 3 weeks before seeking medical supervision ⁶. The report, however, also states that persons with obesity-related conditions should consult their physician before starting a VLCD. Thus, although physicians may be involved in identifying appropriate persons for treatment with a VLCD and for providing medical monitoring after the first 3 weeks, they do not have the same gatekeeping role as their U.S. counterparts. Rossner and Torgerson ⁴⁴ have reviewed the Swedish experience with VLCDs and concluded that such programs can be provided largely by dietitians and nurses, lessening the need for physician involvement. We note that some companies in the United States sell very low calorie diets directly to consumers ⁴³, whom they tell to consult with their physician before dieting. However, medically unsupervised use of these diets falls outside the guidelines recommended by expert panels in the United States.

Very Low Calorie Diet Side Effects

VLCDs are considered safe and effective when used by appropriately selected individuals under careful medical supervision ⁸. The diets are designed for patients with a BMI ≥ 30 kg/m2, a group at increased risk of cardiovascular morbidity and mortality and that also may derive the most benefit from substantial weight loss. In the United States, all candidates for a VLCD are expected to undergo a history and physical examination to determine medical and behavioral contraindications to treatment, as described in previous reviews ⁸. As noted previously, a similar recommendation applies in Europe to individuals who have significant comorbidities ⁶.

Patients in medically supervised VLCD programs in the U.S. are monitored by a physician approximately every 2 weeks during the period of rapid weight loss (i.e., 1.5 to 2.5 kg/wk). During this time, they are at increased risk of gallstones, cold intolerance, hair loss, headache, fatigue, dizziness, volume depletion (with electrolyte abnormalities), muscle cramps, and constipation. These side effects are usually mild and easily managed.

Cholelithiasis has been studied in detail. In an early study, gallstones developed in 25% of patients during 8 weeks of VLCD, and 6% of patients eventually required cholecystectomy. In a second trial, asymptomatic gallstones occurred in ∼12% of patients within 6 months of starting a VLCD, and approximately one-half of these individuals eventually became symptomatic, requiring cholecystectomy. The risk of cholelithiasis can be decreased by administration of ursodeoxycholic acid, including a moderate amount of fat in the diet, and limiting the rate of weight loss to 1.5 kg/wk.

In Europe, VLCDs apparently have not been associated with a higher than expected rate of cholelithiasis. This has been attributed to the inclusion of at least 7 grams of fat in meal replacement regimens sold in Europe, as reported by Festi et al. ⁴⁵.

Unsupervised use of VLCDs can result in serious complications, including sudden death ⁴⁶, ⁴⁷, ⁴⁸, ⁴⁹, ⁵⁰, which have contributed to stricter rules in the United States (where VLCD programs must be managed by a physician) than in Europe ⁵¹. The great majority of fatalities related to VLCDs occurred in the 1970s when dieters consumed products that contained low-quality protein (i.e., hydrolyzed collagen) and were deficient in vitamins and minerals. Of 60 persons who died in the United States, most developed cardiac complications after a loss of ∼30% of initial weight, achieved in an average of 4 months. No deaths were reported in persons who dieted for 8 weeks or fewer.

The SCOOP-VLCD report ⁶ noted that there have been no documented deaths attributable to VLCDs since their inclusion in the early 1980s of high-quality proteins (i.e., milk, egg, or soy). Nonetheless, in the United States, there were six reports of death during this time in persons who consumed the Cambridge Diet (which provided 330 kcal/d at the time) ⁵⁰. Observational data clearly can lead to different conclusions about the safety of a product because of differences in the way the product is used (e.g., duration of use) or in the populations that use it (e.g., lean vs. obese individuals). Thus, although VLCDs seem to be safe when consumed for brief periods without medical supervision, long-term unsupervised use of a VLCD could be associated with significant health complications (as could any hypocaloric, reducing diet).

Rapid weight loss, whether by VLCD or bariatric surgery, increases the risk of developing gallstones, and clinical recommendations advise physicians to inform patients about this risk ⁶, ⁴⁶, ⁵². Gallstone formation has mainly been associated with VLCDs containing low amounts of fat (∼1 g/d) ⁵³, ⁵⁴, ⁵⁵, ⁵⁶, ⁵⁷, and a higher fat content (12–30 g/d) seems to reduce gallstone formation ⁵⁸, ⁵⁹, ⁶⁰, ⁶¹.

Should you use a very low calorie diet to lose weight ?

Most people who need to lose weight should not use a very low calorie diet. For many of them, a low-calorie diet (LCD) may work better (see The Low-calorie Diet (LCD)) ⁴², ⁴⁸.

Very low calorie diets may be used to promote rapid weight loss among adults who have obesity. Health care providers must review risks and benefits on a case-by-case ​basis.

In general, VLCDs are not appropriate for children. In a few cases, they may be used with some adolescents who are being treated for obesity.

Not much is known about the use of VLCDs to promote weight loss among older adults. Some people over age 50 may have medical issues that may not make them good candidates for this type of diet.

How Effective Are Very Low-Calorie Diets ?

If you have a BMI over 30 (which your doctor will call “obese”), then a very low-calorie diet may let you lose about 3 to 5 pounds per week, for an average total weight loss of 44 pounds over 12 weeks.

Losing that amount of weight may improve weight-related medical conditions, including diabetes, high blood pressure, and high cholesterol. But in the long-run, very low-calorie diets aren’t more effective than more modest diets. Once you go off a diet, you need to change your lifestyle, committing to healthy eating and regular physical activity.

What are the health benefits of a Very Low-Calorie Diets ?

A VLCD may allow you to lose about 3 to 5 pounds per week. This may lead to an average total weight loss of 44 pounds over 12 weeks. Such a weight loss can rapidly improve medical conditions linked to obesity, including diabetes, high blood pressure, and high cholesterol.​

The rapid weight loss experienced by most people on a VLCD can be very motivating. Patients who participate in a VLCD program that also includes lifestyle changes may lose about 15 to 25 percent of their initial weight during the first 3 to 6 months. They may maintain a 5 percent weight loss after 4 years if they adopt a healthy eating plan and physical activity habits.

What are the health risks of a Very Low-Calorie Diets ?

Very low-calorie diets are NOT okay for everyone. Talk to your doctor to see if this kind of diet is appropriate for you.

If your BMI is greater than 30, then very low-calorie diets are generally safe when used under proper medical supervision. For people who are overweight but not obese (BMI of 27-30), very low-calorie diets should be reserved for those who have weight-related medical problems and are under medical supervision.

Very low-calorie-diets are NOT recommended for pregnant or breastfeeding women, and are not appropriate for children or teens except in specialized treatment programs. They also may not be OK for people over age 50, either, depending on the potential need for medications for pre-existing conditions, as well as the possibility of side effects.

Doctors must monitor all very low calorie diet patients regularly—ideally every 2 weeks in the initial period of rapid weight loss—to be sure patients are not experiencing serious side effects.

Many patients on a very low calorie diet for 4 to 16 weeks report minor side effects such as fatigue, constipation, nausea, or diarrhea. These conditions usually improve within a few weeks and rarely prevent patients from completing the program.

The most common serious side effect is gallstones. Gallstones, which often develop in people who are obese, especially women, may be even more commonly developed during rapid weight loss. Some medicines can prevent gallstones from forming during rapid weight loss. Your health care provider can determine if these medicines are appropriate for you.

What Are the Other Drawbacks of Very Low-Calorie Diets ?

To be healthy, you need a balance of foods from different food groups. It’s difficult to get good nutrition and feel satisfied on a very low-calorie diet. In addition, consuming as few as 800 calories daily may not give you the energy you need for daily living and regular physical activity, especially if you eat the same foods every day.

Will you regain the weight ?

Although the long-term results of very low calorie diets vary widely, weight regain is common. A randomized trial showed that VLCD-treated patients who lost 14.8 kg regained 50% to 80% of lost weight 18 months after the end of treatment and did not benefit from individualizing the rate of refeeding or using meal replacements during maintenance ⁶².

To prevent weight regain, the very low calorie diet should always be combined with other ways to lose weight and with an active follow-up program. Two studies of exercise to facilitate weight maintenance after a VLCD yielded mixed results ⁶³, ⁶⁴.

For most people who have obesity, the condition is long term and requires a lifetime of attention even after formal methods to treat the obesity end. You may need to commit to permanent changes of healthier eating, regular physical activity, and an improved outlook about food.

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