Most people on semaglutide should aim for 1,200 to 1,800 calories per day, or roughly 500 calories below what their body burns daily. The right number depends on your size, activity level, and how your body responds to the medication. Semaglutide dramatically reduces appetite on its own, which means the bigger challenge for many people isn’t eating less but making sure they eat enough.
What the Clinical Trials Used
The landmark STEP trials that led to semaglutide’s approval for weight loss tested two different calorie approaches. In STEP 1, 2, 4, 5, and 8, participants followed a reduced-calorie diet set at a 500-calorie daily deficit relative to their estimated energy expenditure, combined with 150 minutes of physical activity per week. So if your body burns 2,200 calories a day, you’d eat around 1,700.
STEP 3 took a more aggressive approach: participants ate just 1,000 to 1,200 calories per day as meal replacements for the first eight weeks, then shifted to 1,200 to 1,800 calories of conventional food for the remaining 68 weeks. This trial also ramped physical activity from 100 minutes per week up to 200 minutes. Both approaches produced significant weight loss, but the 500-calorie deficit model is what most prescribers use as a baseline.
How to Find Your Number
Start by estimating how many calories your body burns in a normal day, sometimes called your total daily energy expenditure. Online calculators that factor in your age, sex, height, weight, and activity level can give you a reasonable estimate. Subtract 500 from that number, and you have your daily target. For most adults, this lands somewhere between 1,200 and 1,800 calories.
There is a floor you shouldn’t drop below without medical guidance. Harvard Health recommends women eat no fewer than 1,200 calories per day and men no fewer than 1,500. Going lower risks depriving your body of essential nutrients. This is especially relevant on semaglutide because the appetite suppression can be so strong that some people genuinely struggle to eat enough, particularly during the early weeks or after a dose increase.
Why Protein Matters More Than Total Calories
When you lose weight rapidly, your body doesn’t just burn fat. It also breaks down muscle. On semaglutide, where weight loss can be substantial, preserving lean muscle mass becomes a real concern. The most effective way to protect it is eating enough protein: 1.2 to 2.0 grams per kilogram of body weight each day. For a 180-pound person, that translates to roughly 98 to 164 grams of protein daily.
Hitting those numbers on a reduced-calorie diet means protein needs to take priority at every meal. Lean meats, eggs, fish, Greek yogurt, cottage cheese, and legumes are all efficient sources. If you’re eating only 1,200 to 1,400 calories, protein-dense foods should make up the core of your diet, with vegetables and complex carbohydrates filling in the rest.
Nutrient Gaps to Watch For
Eating less food means getting fewer vitamins and minerals, and the research on this is sobering. A large analysis of over 480,000 adults taking GLP-1 medications found that vitamin D deficiency was the most common nutritional problem, affecting 13.6% of participants after 12 months. Iron deficiency hit 3.2%, B vitamin deficiency 2.6%, and 4% developed anemia from nutritional shortfalls.
A smaller study that tracked the actual food diaries of 69 GLP-1 users found even starker numbers: 72% consumed less calcium than recommended, 64% didn’t get enough iron, and only 1.4% met vitamin D targets. Researchers have called nutritional deficiencies “a common consequence” of GLP-1 therapy. A daily multivitamin is a reasonable safety net, with particular attention to vitamin D, iron, and B vitamins.
How to Structure Your Meals
Semaglutide slows gastric emptying, meaning food sits in your stomach longer than usual. This is part of how the drug works, but it also means large meals can trigger nausea, bloating, and discomfort. Eating smaller, more frequent meals throughout the day is the most effective way to manage this.
A few practical guidelines from gastroenterology research on GLP-1 users:
- Eat slowly and stop before you feel full. Your usual hunger and fullness signals will shift on this medication, and overeating even slightly can cause nausea.
- Favor simple cooking methods. Avoid complex, heavy dishes, spicy foods, and alcohol, all of which can worsen GI symptoms.
- Choose complex carbohydrates like pasta, bread, and crackers over whole grain products and foods high in simple sugars, which can further slow digestion.
- Eat fruit as a snack between meals rather than adding it to lunch or dinner, where it increases meal volume.
- Avoid soups and broths at dinner, as liquid foods in the evening can slow digestion overnight and increase symptoms.
- Don’t lie down after eating. Stay upright and avoid vigorous exercise right after meals.
Fiber and Constipation
Constipation is one of the most common side effects of semaglutide. Fiber helps, but it needs to be increased gradually. Women should aim for at least 25 grams per day and men for 35 grams, from a mix of soluble sources (oats, beans, fruits) and insoluble sources (vegetables, nuts, seeds). One critical detail: increasing fiber without increasing water intake can actually make constipation worse.
Hydration on Semaglutide
Semaglutide can blunt your natural thirst signals, making it easy to become dehydrated without realizing it. A common guideline is to drink half your body weight (in pounds) in ounces of water each day. A 200-pound person would target about 100 ounces. Sip water throughout the day rather than drinking large amounts at meals, which can increase fullness and nausea. Adding sugar-free electrolytes can help, especially during the first few months when GI side effects are most common and fluid losses may be higher.
Adjusting Over Time
Your calorie needs will change as you lose weight. Someone who starts at 250 pounds burns significantly more calories at rest than they will at 200 pounds. Recalculating your energy expenditure every 20 to 30 pounds lost keeps your deficit in the right range. Too large a deficit leads to excessive muscle loss and nutrient deficiencies. Too small a deficit stalls progress.
Many people also find that their appetite fluctuates with dose changes. When you move up to a higher dose, the appetite suppression often intensifies for a few weeks before leveling off. During those windows, focus on nutrient density over volume. Even if you can only manage 1,000 calories on a rough day, make those calories count with protein, vegetables, and healthy fats rather than empty carbohydrates.