Research

Energy balance

Very-low-calorie diets (VLCDs, ~420 kcal/day) produce significantly greater short-term weight loss (approx. 21 kg) compared to moderate caloric restriction (1,200 kcal/day, approx. 12 kg) over 26 weeks, but this advantage is entirely lost by 78 weeks due to rapid weight regain in the VLCD group.

While a very low-calorie diet (around 400-500 calories) will help you drop weight much faster than a standard 1,200-calorie diet in the first 4 months, it does not help you keep it off. In fact, people on the extreme diet regained most of their weight by the end of the year, ending up with less net loss than those who lost weight more slowly. Focus on a sustainable deficit and maintenance strategies rather than extreme speed.

GoodQualifiesHIGH confidence
The VLCD subjects lost significantly more weight than the BDD subjects at all periods through Week 26... VLCD subjects, however, regained weight during the next 26 weeks of weekly therapy and during a 26-week weight maintenance program... Mean weight losses at the end of the maintenance program were 10.94 and 12.18 kg, respectively.
Thomas A. Wadden et al. · Journal of Consulting and Clinical Psychology · 1994

Why this rating

Randomized controlled trial with 49 subjects, clear statistical significance (p<.001) for short-term differences, though sample size is modest.

Source

One-year behavioral treatment of obesity: Comparison of moderate and severe caloric restriction and the effects of weight maintenance therapy.

Thomas A. Wadden et al. · Journal of Consulting and Clinical Psychology · 1994

DOI 10.1037/0022-006x.62.1.165

rct · n=49Cited 307×
Read the paper
DOI resolved against Crossref · corpus check 2026-06-10

This is one finding among thousands. Every one is graded and traced to its source, so you can see what the evidence actually supports. Browse the research →