The effects of weight loss on digestion and energy: fatigue, constipation, and bowel dysfunction.

1. Fatigue

Overview: Fatigue is a common symptom of many diseases. It can refer to objective weakness caused by decreased muscle strength, or subjective fatigue (difficulty/inability to start activity, easy fatigue, mental fatigue, etc.), or overwhelming drowsiness. Studies have shown that the degree of weight loss in people who experience weight loss within 3 months is positively correlated with the occurrence of fatigue symptoms.

Causes: Malnutrition or weight-loss drugs can lead to fatigue in those who are trying to lose weight improperly. Malnutrition and fatigue can interact; fatigue may indirectly restrict food intake by affecting appetite and food consumption, resulting in insufficient intake of nutrients such as protein, thus exacerbating malnutrition and creating a vicious cycle. Weight-loss drugs work by suppressing appetite or inhibiting gastrointestinal absorption, which over time can easily lead to electrolyte imbalance, anorexia, fatigue, and other symptoms.

Prevention and treatment measures: Dietary therapy studies have shown that diets high in omega-3 fatty acids, vitamin D, and high-quality protein, along with increased fruit and vegetable intake, have a positive effect on the treatment of fatigue. Probiotics may also improve fatigue symptoms. Studies have shown that NADH (reduced coenzyme I) and its combination with coenzyme Q10 can improve fatigue symptoms. II. Constipation

Overview: Constipation is a functional gastrointestinal disorder characterized by a group of symptoms including infrequent bowel movements, hard stools, difficulty defecating, prolonged defecation time, anal distension, and a feeling of incomplete evacuation. Globally, the prevalence of constipation is estimated to be between 1% and 80%, significantly impacting the quality of life for those suffering from constipation.

Causes: Constipation caused by poor weight loss is often due to insufficient food intake, insufficient dietary fiber intake, and insufficient water intake caused by excessive dieting. Insufficient food intake can reduce food residue in the intestines through the gastrocolic reflex, weakening the defecation reflex; on the other hand, it can slow down the renewal rate of intestinal cells and weaken their motility. Insufficient dietary fiber intake increases colonic transit time. Insufficient water intake leads to dry and hard stools.

Prevention and treatment measures: (1) Dietary intervention: Increasing dietary fiber intake can improve constipation. It is recommended that patients with constipation consume 25-35g/day of dietary fiber. Foods rich in dietary fiber include: grains, vegetables, fruits, etc. Increase water intake, and it is recommended to drink 1.5-2.0L/day. (2) Drug treatment: Bulk-forming laxatives soften stool by retaining water in the stool, such as polyethylene glycol-4000. Osmotic laxatives can promote the secretion of water and electrolytes by creating an osmotic pressure gradient in the intestinal lumen. Drugs include lactulose, mannitol, etc. Stimulant laxatives include bisacodyl, phenolphthalein, etc., which have a fast onset of action. Prokinetic drugs such as mosapride and prucalopride can increase intestinal motility. (3) Other therapies: Biofeedback therapy is an effective and side-effect-free method that uses computer assistance to help patients establish normal physiological functions of defecation. III. Gastrointestinal dysfunction

Overview: Gastrointestinal problems caused by poor weight loss are numerous and complex, the most common being bloating and abnormal bowel movements (including diarrhea and constipation). Functional bloating manifests as recurrent episodes of abdominal fullness, pressure, or a feeling of gas buildup. Diarrhea is defined as a significant increase in the frequency, volume, and water content of bowel movements compared to normal.

Causes: Besides organic lesions, special diets, misuse of meal replacement products, laxatives, and emotional stress during weight loss are common factors leading to diarrhea and constipation. Tension and anxiety can affect normal gastrointestinal function. Gastrointestinal activity is jointly controlled by the enteric nervous system and the central nervous system; abnormalities in either system can lead to gastrointestinal symptoms, i.e., the brain-gut axis system. Furthermore, special diets such as the ketogenic diet and the Copenhagen diet may lead to insufficient dietary fiber intake, causing constipation or diarrhea due to intolerance.

Diagnostic criteria: Functional bloating requires symptoms to have been present for at least 6 months, meeting the criteria for the past 3 months, and excluding irritable bowel syndrome. Chronic diarrhea is defined as symptoms lasting more than 4 weeks. Functional constipation, according to the Rome III criteria, requires indicators such as deformed stools, a feeling of incomplete evacuation, and a feeling of anal obstruction.

Prevention and treatment: Western medicine treatment mainly focuses on regulating gastrointestinal motility, correcting visceral hypersensitivity, and regulating gut microbiota. A balanced diet and changes in unhealthy habits can effectively prevent functional bloating; the intake of gas-producing foods (such as onions, raw garlic, potatoes, and beans) should be reduced. For functional diarrhea, attention should be paid to correcting dehydration, supplementing with oral rehydration salts (ORS), and avoiding intestinal irritants (such as sugary drinks, dairy products, and caffeine). Long-term use of probiotics or prebiotics can help rebuild the gut microbiota.