Severe caloric restriction (generally defined as eating less than 800 kcal/day) can be an effective weight-loss strategy, but it is difficult to maintain and comes with a number of risks, including fatigue, dizziness, hair loss, and bone loss.

The study

In this randomized controlled trial, 101 obese postmenaposal women were told to cut their caloric intake by either 25–35% (moderate) or 65–75% (severe). The moderate dieters followed the Australian Guide to Healthy Eating for 12 months, while the severe dieters ate a meal replacement for 4 months before switching to the same diet (in calories and nature) as the moderate group for the remaining 8 months. Both groups ate 1 gram of protein per kilogram of body weight (1 g/kg / 0.45 g/lb) per day. Weight loss was used to monitor dietary adherence. Researchers measured body composition at baseline and months 4, 6, and 12.

The results

Both groups lost weight, but 82% of severe dieters lost at least 10%, compared to 27.5% of moderate dieters. The severe dieters also lost more fat, lean mass, and hip bone mineral density. This BMD loss is a concern, though it must be weighed against the benefits of weight loss. Further investigation of the long-term effects of severe dietary interventions is needed.


Of the original 101 participants, 16 dropped out for various reasons, such as feeling unwell or being dissatisfied with the diet or amount of weight loss. Of those 16, only 4 were severe dieters, maybe because severe dieters were losing more weight. Interestingly, the participant who lost the second highest percentage of body weight was among the moderate dieters.

Every month we summarize over 150 of the most noteworthy health and nutrition studies. Other health categories related to this summary include:Try Examine+ for free to view the latest research in 25 health categories and the entire Study Summaries archive, access our Supplement Guides, and unlock the Examine Database. Plus, earn continuing education credits!

Get free weekly updates on what’s new at Examine.

This Study Summary was published on August 6, 2020.