How Many Calories To Lose Weight With Phentermine?

how many calories to lose weight with phentermine

Counting calories is a good way to limit your food intake while you’re trying to lose weight with phentermine.

However, there is a lot of debate about how many calories you should be eating to achieve weight loss with phentermine, so we’re here to make everything clearer!

So, read on to find out how to cut calories smartly and lose weight with phentermine!

What Are Calories?

Let’s start from the beginning: a large calorie (kcal) is the amount of energy required to raise one kilogram of water by one degree Celsius.

In terms of food, that means that if burned, the food we consume has the power to heat water in this way through the energy it releases.

When we eat, the calories provide the energy our bodies need to perform all daily tasks, from breathing to running and everything in between.

We all require a certain number of calories each day, but too many calories means that the unused energy is stored as fat, leading to weight gain.

So, The Fewer Calories, The Better?

Definitely not! This is one of the biggest diet myths out there.

If food is our fuel, too few calories means that your body is running on fumes, so it doesn’t have the energy to do everything it needs to, which means that losing weight is NOT a priority.

To lose weight, your body needs to burn fat and build muscle, but each pound of lean muscle in your body requires 50 to 100 calories to keep going.

In comparison, each pound of fat only requires about 3 calories daily.

If your body doesn’t have enough calories coming in, then it prioritizes feeding the fat to sustain itself for the future rather than feeding the hungry muscle cells.

On the scale, it may still appear that you’re losing weight, but it’s the wrong way to go about it; eating too little and losing precious muscle often leads to a yo-yo dieting cycle of losing and gaining weight.

This is because losing muscle and forcing your body to conserve fat slows down metabolism and means that when you inevitably start to consume more calories, your body will be ill-equipped to burn them off, and the scale will start to move up again.

As with pretty much everything related to what’s best for your body, you need to find a balance – too much or too little of anything will always cause problems.

However, finding the perfect number of calories can be tricky, especially as we are all so different.

To lose weight, factors such as your start weight, activity level, and age will all play a part in determining your metabolic rate and, therefore, how many calories you can consume and still achieve weight loss.

If you’re particularly active, then your calorie allowance per day will be higher, but you shouldn’t use exercise as a way to create a ‘calorie deficit’ – i.e., where you are burning more calories than you’re eating.

Your body is constantly burning calories just doing everyday tasks, especially if you have the lean muscle to help you out.

If you’re over-exercising, your body is left in the same position as if you were not eating enough calories.


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Building muscle will be put on the back burner to preserve fat to keep your body going on fewer calories. So, despite what you may have heard, a calorie deficit does not mean faster weight loss. 

Furthermore, over-exercising isn’t something you can sustain for very long – you’ll become burned out and may risk injury, which might make you give up altogether.

Instead, just aim to build muscle with weight training three times a week for around 15 minutes a time, and try to do cardio for around an hour a time, at least three days a week.

And, if you overeat and end up consuming too many calories, then you also shouldn’t use exercise as a way to eat more calories – the gym won’t help you undo a bad diet!

How Many Calories Should I Eat Each Day?

How Many Calories Should I Eat Each Day

When you are first prescribed phentermine, your doctor should give you an idea of how many calories to eat each day to lose weight.

While the best way to determine the number of calories you should eat each day is to have your basal metabolic rate analyzed by your doctor or health professional, you can calculate an approximate figure using online sites by entering your age, height, weight, and gender.

Using several different sites will give you a more reliable number.

Then you can factor in any activity you do throughout the week to assess how many calories your body needs to lose weight.

To give an example, we entered the details of a 40-year-old woman of 5’4” who is 200lbs.

With little to no exercise, she should aim for 1,600 calories per day to lose weight, but if she exercises four times per week, then her allowance is an average of around 1,800 per day.

Once you have accounted for the average amount of activity you do each week, you will have a more personalized figure of the daily calorie allowance you should aim for to lose weight.

This is an approximation, so if you feel that it’s too high or too low, you should ask your doctor for advice.

However, the general consensus is that women should never consume fewer than 1,200 calories per day and men no fewer than 1,500 calories.

This absolute lower limit should not be taken as a number to aim for, especially if you are very active or very tall, as you would need more calories than that to sustain yourself.

But, as you lose weight, you should also be sure to recalculate your calorie allowance to ensure that you’re not eating too much following a period of weight loss, which might cause your weight to plateau.

Similarly, if you’ve become more active, your faster metabolism might need more fuel to keep it going, so you should always be sure to reassess your calorie allowance throughout your weight loss journey with phentermine.

Depending on how many calories you’re used to eating, your calorie limit may seem low, but phentermine will suppress your appetite, making it possible to reduce your calorie intake without feeling hungry.

However, as many people have shared in our phentermine support group on Facebook, the appetite-suppressing effects of phentermine can sometimes be excessive, to the extent that phentermine users find it hard to reach the 1,200 limits each day.

If this is the case for you, you should not make up the extra calories with unhealthy foods full of empty calories like cakes and chips. Instead, you should take the opportunity to eat healthy but calorific foods, such as nuts and avocados.

These foods are full of healthy fats and many essential nutrients, which can help to boost weight loss while also helping to top up your calorie allowance.

This extreme appetite suppression should subside within a few days, but if you find that you continue to struggle to reach the 1,200-calorie minimum, then you should speak to your doctor about the possibility of lowering your dosage.

Alternatively, if phentermine isn’t suppressing your appetite as much as you had hoped and it’s difficult to stick to your limit, then we recommend adding the weight loss supplement Phen Caps to your daily routine.

Phen Caps are the leading phentermine alternative, so they can be taken instead of phentermine to help you lose weight, but they can also be taken alongside phentermine to boost the effects.

With the help of Phen Caps in combination with phentermine, you will experience a suppressed appetite and fewer cravings, meaning that you won’t feel so deprived of sticking to your calorie limit.

But Remember, Not All Calories Are Equal

Counting calories works for many dieters because they can see more easily how much they can eat of certain food and when they’ve reached their daily limit.

However, it’s important to recognize that not all calories are created equally; avocados may be high in calories, but they are also full of good fats, which boost weight loss, and diet soda may be calorie-free, but it’s far from healthy. 

So, take all things into consideration when choosing what to eat, as calories are only part of the picture. In addition to counting calories, you should aim for 20-35% of these calories to be protein to help you build lean muscle and keep you feeling full. 

You should also aim to eat 25g of fiber each day and plenty of fresh fruit and vegetables too.

You should ‘spend’ the calories you have each day wisely – a candy bar is full of empty calories, which will use up a lot of your daily allowance but give you nothing in return in terms of nutrients, and it won’t curb hunger for very long, either.

Often when counting calories, it can be easier to choose pre-packed snacks or low-calorie snacks.

Still, you should try to reduce the number of processed foods you eat as these might have the right amount of calories, but they won’t give you the benefits you would get with fresh, unprocessed foods.

Also, these types of foods often make up for reduced calories with saturated fat, artificial ingredients, or added sugar – three of your biggest weight loss enemies!

Planning meals in advance and home cooking are healthy habits that help you to stick to your new way of eating.

Plus, you can change ingredients to reduce the calorie content, meaning that eating the foods you love on phentermine is still possible.

Here you can see that there is no one-size-fits-all amount of calories that guarantees weight loss with phentermine.

Instead, you have to find the right number of calories for YOU to get the balance right and drop those unwanted pounds without feeling deprived! How many calories do you eat per day? Let us know by commenting below!

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  1. I’m using my fitness pal to track my food 1200 calories a day but I don’t know whatvti set my micronutrients at.
    other people are saying to do intermittent fasting 16.8 but how do you know what to eat

    1. Hi Kathy,

      Many users have found success with intermittent fasting while on phentermine.

      To keep hunger at bay, you must focus on filling up foods high in protein and fiber, as this winning combination will leave you full for hours. So, be sure to eat lean meat, fish, eggs, and other healthy protein sources, as well as plenty of fiber-packed foods, such as whole grains, legumes, fruit, and vegetables.

      Just like your metabolism, your hunger isn’t set in stone, and one of the best ways to reprogram your hunger levels is to concentrate on relieving stress in your life and ensure that you get at least seven hours of sleep each night.

      Stress and a lack of sleep both heighten appetite and cause hunger signals to become confused.

      Hope that helps! You are also more than welcome to join our official Facebook support group so you can connect with other phentermine users today:

      Best regards,


  2. Hi! I just started taking phentermine a few day’s ago and I’m definitely not eating a lot throughout the day because I never have the appetite. I haven’t counted but I am sure I’m lower than my daily calorie goal. Is it really that important to hit your calorie goal? Does this extreme appetite suppression go away as you keep taking the medication?

    1. Hi Brittany 🙂 Yes, it’s important that you hit your calorie goal – plus or minus a couple hundred calories – most days so that your body has the fuel it needs to power you through the day. Right now (while you feel like you have a lot of control over your appetite) is a great time to work on developing healthy habits that you can stick to long-term like meal planning, eating more whole grains and snacking on fruits & veggies. That being said, yes – most patients report that appetite suppression is strongest the first few days or weeks with phentermine and then becomes slightly weaker as treatment goes on, so your appetite will likely increase over time. Best of luck on your weight loss journey!

  3. I have been on highest dose on phentermine havent lost no weight been 6 days i work out 4 to 5 days out the week 1 hour max what am i doing wrong dr tolk split pills in have until after my 7th day take a full pill for rest of the month the pill is supressing my appetite but i feel kind drowsy I’m 276Lbs what am i doing wrong i eat 3 x a day clean eating 1.200 calories

    1. Hi Jasmine – sorry to hear phentermine isn’t doing much for you 🙁 We’d suggest that you talk to your prescribing physician about the drowsiness and lack of weight loss. He or she is best able to evaluate what may be getting in the way of your weight loss and suggest small tweaks to help, or even switch your prescription to another medication that may work better for you. Plus, he or she needs to know about the drowsiness ASAP since that isn’t a common reaction. It may also help to increase your caloric intake a little bit given that you’re working out consistently and 1200 calorie/day is considered a bare minimum. An app like MyFitnessPal or LoseIt can be helpful for determining more accurate calorie needs. Best wishes!

  4. Thanks! I love your site. But can you explain more about who it works with a slow metabolism? is there any problem?

  5. I have been taking a gradual increased dose of phentermine for 3 months. I started with 15mg for 30 days, the increased to 30mg for 30 days and have now begun taking 37.5mg. I been on the highest dose for one week now. My overall weight loss totals 9lbs on average but fluctuates between 7 and 11 depending on the day. By this time I had expected to down 15-20. Admittedly I don’t exercise as often as I should and I’ve just started a workout routine but I don’t overeat and I don’t eat processed or high sugar foods. Any suggestions on how I can get improved results?

    1. Hi Betsy!

      All bodies and metabolisms are different. It could be because of age, genetics or other factors, but not everyone loses weight at the same rhythm. We suggest you keep focusing on lifestyle changes; those are the only ones that will make a permanent difference, long after your treatment is done. Better nutrition and more exercise are crucial to long-term weight loss and avoiding the dreaded weight gain after your phentermine treatment or diet is over.

      Besides that, you should get in touch with a weight loss specialist: a nutritionist, for example, could help you plan out a balanced long-term diet. If you feel that despite all your efforts, you are not losing weight (or not losing as much as you should) then we suggest contacting your primary care physician to check for thyroid issues (hypothyroidism makes it really hard to lose weight, for example) or other underlying conditions that might affect weight loss.



  6. I have been taking this, have a hard time reaching my 1200 goal but I have lost 9 pounds since I’ve been on this but now my scale is slowly creeping back up. I was at a 10 pound weight loss. Any reason for that? It’s been like this for a week now.

    1. Hi Ricki, thanks for your comment! It’s normal for your weight to go up and down a couple of pounds during your weight loss journey due to hormonal changes, water retention, etc. As long as the overall trend is downwards, you’re doing great! If, on the other hand, the scale keeps creeping up and you’re still eating very little, it may be that your body is trying to hold onto the fat just because it feels like you’re in starvation mode. As counter-intuitive as it sounds, eating more may actually help you start losing weight again. If you really don’t have the appetite for all three meals, consider a meal replacement shake for one meal. It may also be worth it to weigh and/or measure your portions for a little bit so that you know you’re estimating calories accurately. Good luck!

  7. I was told to eat 1200 calories a day and to stop lifting weights. I have no problem trying to add fasted cardio in the morning but the fact that I was told to only eat 1200 calories really bothered me. I lifts weights 4 times a week and will up my protein but I feel like the Dr. Who prescribed me this is trying to make me skinny fat. What is the best way to keep my muscle and lose fat. Even if I can’t build it right now I don’t want to lose what I have.

  8. Thanks! I was told to consume 1650 cal a day and after reading so many blogs and reviews of people eating nothing I was worried I would be eating to much! I’ve broken my calories down to macros, 140g carbs, 140g protein and 30g of fats and I will change and have higher fat days and lower carb days depending on my exercise! Hopefully this drug and my nutrition will help me reach my goals!

    1. Hi Jessica,
      We’re so glad we could help! Best of luck on your phentermine journey!!