Are long-term FAD diets restricting micronutrient intake? A randomized controlled trial.

The micronutrient adequacy of common fad diets is rarely assessed. We compared a high-fiber diet [HF] with a low-carbohydrate diet [LC] to assess their effects on body weight and micronutrient adequacy. One hundred and seventy-three adult males and females with or without diabetes with a mean body mass index of 36 kg/m were randomized to either a HF or LC diet. Differences in anthropometrics, blood lipids, glucose, blood pressure, and micronutrient consumption between groups were assessed after 52 weeks. Differences between groups a priori were assessed using independent tests and chi-squared tests. Post hoc differences in nutrient consumption between groups while controlling for gender were assessed using factorial analysis of variance. After 52 weeks, LC dieters ( = 24) retained weight loss better than their HF counterparts ( = 30) ( = .06). LC dieters consumed more vitamin K (mcg) [HF = 124.0 ± 15.0; LC = 220.0 ± 39.1;  = .025] and vitamin B12 (mcg) [HF = 3.1 ± 0.3; LC = 4.1 ± 0.4;  = .026]. The HF group consumed more folate (mcg) [HF = 479.9 ± 34.0); LC = 333.8 ± 22.1;  < .001], magnesium (mg) [HF = 353.1 ± 17.4; LC = 281.1 ± 18.0;  < .001], and iron (mg) [HF = 14.6 ± 0.8; LC = 10.7 ± 0.6;  < .001. Both groups consumed less than the respective EAR for vitamins D and E and less than the AI for potassium. While a LC diet may be more effective for long-term weight loss, both diets were deficient in micronutrients.