This study revealed a high prevalence of overweight, obesity and central obesity among the enrolled 120 patients, close to that reported for patients with MS in the same unit in a prior study [5]. The prevalence of overweight and obesity is higher than that reported by Marck et al. [27]. Mean waist circumference is also higher than that reported by Drehmer et al. [28], indicating a higher risk of metabolic complications than the other finding [19]. The observed higher prevalence in this study than in theirs can be attributed to the overconsumption of macronutrients, low intake of dietary fibers and the sedentary nature of most of the patients. The mean 24-h energy, carbohydrates, proteins, and fat consumption were higher in our study than that reported by Armon-Omer et al. [29] and the lower fiber intake accounts for the difference in mean BMI between the two studies (27.7 ± 5.7 kg/m2 and 25.0 ± 4.4 kg/m2, respectively).

The current trial revealed that counseling improved the IG anthropometry, food choices and most nutrients’ intake and adequacy compared to the CG. Counseling significantly increased the practice of sports, sun exposure and reduced the time spent on sedentary activities.

The effect of the intervention on weight, BMI, and waist circumference differed in the two sex groups, indicating an intervention–sex interaction. Nutrition counseling significantly helped female patients with MS improve their weight, BMI, and waist circumference. It did not significantly affect the three measures in males. An explanation for the differential effect is that the number of males was less than half that of females (33 and 87, respectively); moreover, males had lower mean BMI and waist circumference than females (P < 0.05) did because most of men (60.6%) started at a normal weight; approximately one-third of males had the more severe forms of disease (SPMS and PPMS), and that was 6.9% for females (P = 0.002); they had earlier onset of disease, longer duration, and higher EDSS (P < 0.05) (Refer to supplementary files). Inclusion of disease factors in the analysis revealed marginally significant interaction between intervention and MS subtype in males but not in females (P = 0.056).

The PPA showed that more weight was lost by compliant overweight (P = 0.000) and obese patients (P = 0.000) after the excluding non-compliers who diluted the change observed in the ITTA. Additionally, the PPA highlighted the significant change in the compliant male’s waist circumference (P = 0.043) in contrast with the insignificant change revealed by the ITTA. (P = 0.280) (Refer to supplementary files). The link between the nutritional status and the clinical condition of this group requires further research. A few findings have revealed that overweight and obesity impair the physical and mental health of patients with MS [30]. Moreover, high BMI and waist circumference in patients with MS may exacerbate disease symptoms and the accumulation of disabilities [31, 32].

Per the pre-intervention assessment, dietary fiber was consumed at less than the acceptable levels (8.7 ± 4.6 g/day in all enrolled patients, 8.0 ± 4.1 in females and 10.6 ± 5.2 in males). Nutrition counselling induced significant improvement in fiber intake in the IG from 8.6 ± 5.2 g to 21.0 ± 8.3 g (P = 0.000), and the level of intake of males (27.0 g) and females (20.9 g) became close to the minimum recommended amount compared with the 2020–2025 Dietary Guidelines (22–28 g for women and 28–34 g for men over the age of 19) [33]. Thus, the emphasis on eating fiber-rich foods should increase. High-fiber and low-caloric dietary intake may reduce disease severity and suppress inflammatory conditions in patients with MS [34]. Furthermore, energy intake and dietary fibers are good predictors for EDSS and anthropometric indices (BMI and percentage of body fat) [34].

Regarding micronutrients, the intake of sodium, potassium, calcium, phosphorous, magnesium, iron, zinc and copper and vitamins A, C, B1, and B2 intake was comparable in the IG and CG in the pre-counseling assessment (P > 0.05). Those intakes were lower than the RDA for all nutrients except sodium, which was much higher than the RDA, and phosphorous and copper which were slightly higher than the RDA [17]. The lower intake of calcium, magnesium, zinc, and iron was consistent with finding in Armon-Omer et al. [29].

Counseling also improved micronutrient intake, ANCOVA analysis revealed a significant increase in the consumption of potassium, magnesium, and vitamin C and a decrease in that of sodium, phosphorus, and zinc (P < 0.05). Impairments in micronutrient intake might be of clinical significance in MS because they contribute to existing symptoms, such as muscle wasting, weakness, fatigue, and muscle spasms [20, 35]. The observed effect is attributed to the improved dietary habits, decreased sedentary hours, and increased physical activity. The IG significantly increased their intake of milk, vegetables and fruits and decreased their intake of grains, added sugar and fat (P < 0.05). Milk is an excellent source of many vitamins and minerals, including vitamin B12, calcium, riboflavin, and phosphorus. Milk is often fortified with other vitamins, especially vitamin D [36]. Vegetables and fruits are good sources of vitamins and minerals including vitamin C, carotene, calcium, magnesium, iron, and potassium [37]. Minerals homeostasis plays a fundamental role in the regulation of the CNS functions. In addition, mineral deficiencies have been found in the serum of patients with MS, namely, iron, magnesium, and zinc [35, 38, 39]. These imbalances have been linked to demyelination, perhaps involving oxidative stress [40]. Lower serum zinc levels in patients with MS are commonly observed. Zinc plays a critical role in modifying neuronal excitability and synaptic plasticity [39, 41].

Sodium was consumed in very large amounts by the IG and CG (3222.7 mg and 3274.8 mg/day, respectively). This consumption was higher than the 2300 mg recommended by the 2020–2025 Dietary Guidelines for individuals aged older than 19 years [33]. It was also higher than the mean sodium intake reported in the Armon-Omer et al. (2392.66 mg) [29]. Kleinewietfeld suggested increased dietary salt intake as an environmental risk factor for the development of autoimmune diseases by inducing pathogenic cells and related proinflammatory cytokines [42]. Those cells have been shown to be involved in the development of MS [43]. Although the evidence linking high salt intake and MS is contradictory, combining the DASH diet with low sodium intake might benefit individuals with MS. It also improves the vascular health of patients with MS [6].