Calorie-restricted diets can lead to common nutritional deficiencies if diet quality is not monitored.

noli's read

The idea that calorie restriction increases the risk of deficiencies is strongly supported by research. When total food intake decreases, the probability of meeting recommended requirements for micronutrients (vitamins and minerals) mechanically drops, a phenomenon documented in analyses of commercial diets. Organizations such as Harvard Health confirm that highly restrictive diets or the elimination of entire food groups require special attention to avoid these shortfalls. It is not restriction itself that is 'dangerous,' but the lack of nutritional density associated with an excessive reduction in portions. The most frequently observed deficiencies include iron, vitamin B12, magnesium, and vitamin D, which is corroborated by clinical observations. The advice is therefore globally accurate and reflects a consensus in nutrition: nutrient quality is paramount, especially when caloric volume is reduced.

the sources

No named source held this one up — that absence is part of the verdict.