This study will see if a low-cost dietary plan, based on the standard dietary guidelines of the American Society for Metabolic and Bariatric Surgery (ASMBS) and using locally available foods, can help patients lose weight and keep their lean body mass after bariatric surgery. It will also check if this plan can maintain healthy levels of important nutrients such as vitamin B12, iron, and vitamin D.

Patients who have undergone bariatric surgery will be randomly assigned to follow either the low-cost diet or the regular hospital diet. Their weight, body composition, and nutrient levels will be tracked at baseline, and at 1, 3, and 6 months after surgery.

The aim is to find out if this simpler, affordable diet, which follows international standards, works as well as the regular plan while being easier for low-income patients to follow.

Obesity is a growing global health problem and is recognized by the World Health Organization (WHO) as a leading cause of preventable disease. It is a complex, long-term condition influenced by multiple factors, and treatment options range from lifestyle changes to medications and surgery. Bariatric surgery is currently the most effective long-term treatment for morbid obesity. It not only helps in significant weight loss but also improves obesity-related health problems such as type II diabetes, hypertension, and obstructive sleep apnea, while improving quality of life.

Among the various surgical techniques, Roux-en-Y gastric bypass (RYGB), sleeve gastrectomy (SG), and one-anastomosis gastric bypass (OAGB/MGB) are the most commonly performed. However, these surgeries can lead to reduced absorption of essential nutrients because they bypass parts of the intestine where vitamins and minerals are absorbed. Nutrient deficiencies, particularly in vitamin B12, iron, and vitamin D, are common after bariatric surgery. Therefore, structured dietary management and supplementation are essential after surgery to prevent these deficiencies and preserve lean body mass (LBM).

Standard dietary recommendations from the American Society for Metabolic and Bariatric Surgery (ASMBS) suggest a gradual progression from liquids to solid foods, adequate protein intake (1.0-1.5 g/kg), and lifelong use of vitamin and mineral supplements. However, in countries like Pakistan, where 45% of the population lives below the international poverty line, the standard postoperative diet often includes costly imported supplements like whey protein, which are unaffordable and hard to access for most patients, particularly those from rural areas. This creates barriers to dietary compliance and worsens clinical outcomes.

Adequate protein intake plays a key role in preserving lean body mass and improving recovery after bariatric surgery. Nutritional deficiencies, particularly in vitamin B12, iron, and vitamin D, remain prevalent after bariatric surgery and require targeted nutritional strategies.

In response to these challenges, this study introduces a low-cost dietary plan based on ASMBS guidelines using locally available, affordable foods to meet protein and micronutrient needs. It aims to compare this plan with the conventional high-cost hospital diet to determine whether it can effectively promote weight loss, maintain lean body mass, and prevent micronutrient deficiencies. By aligning with international standards while addressing local socioeconomic constraints, this approach could improve patient adherence, nutritional outcomes, and overall recovery following bariatric surgery.

Inclusion Criteria:

• Able to give informed written consent
• Adults between the ages of 18 and 65 undergoing primary bariatric surgery (Roux-en-Y gastric bypass, sleeve gastrectomy, or OAGB)

Exclusion Criteria:

• Patients having revision bariatric surgery
• Patients with recognized diseases related to micronutrient supplementation
• Patients with pre-existing gastrointestinal, metabolic, or endocrine disorders that impair nutrient absorption