8.3 MNT for Overweight, Obesity, and Underweight
Key Takeaways
Losing 5-10% of initial body weight over about 6 months improves blood pressure, glucose, and lipids and is a realistic first goal for adults with obesity.
Asian cut-offs for central obesity are a waist circumference of 90 cm or more in men and 80 cm or more in women.
Behavior therapy for weight loss uses self-monitoring, goal setting, stimulus control, problem solving, and relapse prevention.
After bariatric surgery, patients progress through liquid, pureed, soft, and regular stages, aim for adequate protein, and need lifelong vitamin and mineral supplements such as vitamin B12, iron, calcium, and vitamin D.
For underweight adults, adding about 500 kcal/day through frequent, energy-dense meals and snacks supports a gain of roughly 0.5 kg per week.
The table of specifications includes computing a weight control diet and the nutrition management of obesity and underweight. The 2025 FNRI Updating Survey found that nearly one in two Filipino adults (44.5%) was overweight or obese, so weight management is a core skill.
Classifying Body Weight
| Measure | Cut-offs |
|---|---|
| BMI, WHO international | Underweight below 18.5; normal 18.5-24.9; overweight 25.0-29.9; obese 30.0 and above |
| BMI, Asia-Pacific | Normal 18.5-22.9; overweight (at risk) 23.0-24.9; obese class I 25.0-29.9; obese class II 30.0 and above |
| Waist circumference (Asian) | Central obesity at 90 cm or more in men and 80 cm or more in women |
| Percent DBW | 120% or more obese; 110-119% overweight; below 90% underweight |
| Children 5-19 years (WHO BMI-for-age) | Overweight above +1 SD; obese above +2 SD; thin below -2 SD |
Waist circumference and waist-to-hip ratio identify visceral fat, which carries more metabolic risk than fat on the hips and thighs.
Causes and Consequences
Causes: sustained positive energy balance from energy-dense diets, sugar-sweetened beverages, large portions, and physical inactivity, influenced by genetics, sleep, stress, medications (corticosteroids, some antipsychotics), and endocrine conditions (hypothyroidism, Cushing's syndrome, polycystic ovary syndrome).
Consequences: type 2 diabetes, hypertension, dyslipidemia, metabolic dysfunction-associated fatty liver disease, gallstones, obstructive sleep apnea, osteoarthritis, gout, infertility, and some cancers.
Setting Goals
- A 5-10% loss of initial weight within about 6 months is the usual first goal and produces meaningful health benefits.
- A safe rate is about 0.5-1 kg per week, from a deficit of about 500-1,000 kcal/day.
- After 6 months, the focus shifts to weight maintenance, which is often harder than weight loss.
Dietary Approaches
| Approach | Description | Notes |
|---|---|---|
| Balanced low-calorie diet | TER calculated from DBW, or about 500-1,000 kcal below current intake | Most practical; follows Pinggang Pinoy proportions |
| Common energy levels | Often 1,200-1,500 kcal/day for women and 1,500-1,800 kcal/day for men | Adjust to the individual |
| Very-low-calorie diet | Below about 800 kcal/day | Only with medical supervision; risk of gallstones and electrolyte problems |
| Meal replacements | Formula shakes or bars replacing one or two meals | Help portion control |
| Lower-carbohydrate or lower-fat patterns | Different macronutrient mixes | Long-term results are similar; adherence matters most |
| Time-restricted eating | Eating within a fixed daily window | Works mainly by reducing total intake |
Practical counseling points for Filipino diets:
- Use Pinggang Pinoy: half the plate vegetables and fruit, one-third rice or other Go foods, one-sixth fish, meat, or legumes.
- Control rice portions and choose brown rice, corn, or root crops sometimes.
- Replace sugar-sweetened drinks (soft drinks, sweetened iced tea, milk tea) with water.
- Choose grilled, steamed, or boiled dishes (inihaw, pinasingaw, nilaga) instead of fried ones.
- Plan for fiestas and celebrations, where large portions and fatty dishes are common.
Physical Activity
- At least 150-300 minutes per week of moderate aerobic activity, or 75-150 minutes of vigorous activity, plus muscle-strengthening activity on 2 or more days.
- More activity (about 200-300 minutes per week) helps maintain weight loss.
- Reduce sitting time and increase everyday movement.
Behavior Therapy
| Strategy | Example |
|---|---|
| Self-monitoring | Food diary, step counter, weekly weighing |
| Goal setting | "Walk 30 minutes, 5 days this week" |
| Stimulus control | Keep snacks out of sight; eat only at the table |
| Problem solving | Plan healthy choices at family gatherings |
| Cognitive restructuring | Replace "I ruined my diet" with "I can get back on track at the next meal" |
| Social support | Involve the family in meal changes |
| Relapse prevention | Identify high-risk situations and plan responses |
Medication and Surgery
- Anti-obesity medications may be considered for adults with BMI of 30 or more, or 27 or more with weight-related conditions (lower thresholds are used in some Asian guidelines). Examples include orlistat, which blocks fat absorption, and GLP-1 receptor agonists such as liraglutide and semaglutide, which reduce appetite.
- Bariatric surgery (sleeve gastrectomy, Roux-en-Y gastric bypass) is considered for severe obesity, usually BMI of 40 or more, or 35 or more with comorbidities, with lower thresholds often applied to Asian patients.
Nutrition after bariatric surgery:
- Diet progression: clear liquids, then full liquids, pureed, soft, and finally regular foods over several weeks.
- Small portions eaten slowly; stop at the first sign of fullness.
- Protein first at meals, often about 60 g/day or more.
- Drink fluids between meals, not with them, to avoid dumping and early fullness.
- Lifelong supplements: multivitamin with minerals, vitamin B12, iron, calcium citrate with vitamin D, and thiamin when vomiting occurs.
Childhood Obesity
For growing children, the goal is often to slow weight gain or maintain weight while height increases, rather than strict weight loss. Family-based changes work best: fewer sweetened drinks and fast food, more fruits and vegetables, regular meals, less screen time, and at least 60 minutes of daily activity.
Underweight
Underweight (BMI below 18.5) may reflect poor intake, food insecurity, increased needs, or disease such as tuberculosis, hyperthyroidism, cancer, HIV, malabsorption, depression, or an eating disorder. Assess and treat the cause first.
High-energy, high-protein plan:
- Add about 500 kcal/day for a gain of about 0.5 kg per week.
- Serve 5-6 small meals and snacks rather than 3 large meals.
- Add energy-dense foods: nuts, peanut butter, eggs, milk, oils, avocado, and root crops.
- Use oral nutrition supplements between meals if needed.
- Add resistance exercise so that weight gained includes muscle.
A 40-year-old woman weighs 90 kg and has hypertension and prediabetes. What is the most appropriate initial weight-loss goal?
Reach her desirable body weight within 3 months
Lose 15 kg in the first month using a 600 kcal/day diet
Lose 4.5-9 kg (5-10% of body weight) over about 6 months
Maintain her current weight and rely on medication
Six months after Roux-en-Y gastric bypass, a patient has fatigue and macrocytic anemia. Which deficiency is most likely, and why?
Vitamin K, because the colon was bypassed
Vitamin B12, because less acid and intrinsic factor are available after the bypass
Vitamin C, because fruit and vegetable intake falls sharply after bariatric surgery
Zinc, because the terminal ileum was removed
An underweight college student (BMI 17.2) with no underlying disease wants to gain weight. Which plan is most appropriate?
Three large meals daily with sugary soft drinks
A high-protein diet with no change in total energy intake, relying on protein shakes after every meal
Appetite stimulants without diet changes
About 500 extra kcal/day from frequent energy-dense meals and snacks, with resistance exercise
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