Foods To Avoid While Taking Phentermine (and why)

January 9, 2024 |

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I feel it’s imperative I discuss this topic – after writing on foods to eat when taking phentermine.

How about foods to stay away from?

Well, did you know that as much as 84% of a phentermine dose could be excreted, unchanged, by your kidneys within just 24 hours in an acidic urinary pH ranging from 5.5 to 6.0, but only around 48% might be excreted over the same period with an alkaline urinary pH ranging from 7.5-8.0?

Because you want to make the drug more effective, you should also try to keep it in your body for a longer time. By getting excreted at a much faster rate with an acidic urinary pH, you can easily lose its effects for a shorter time.

That’s why it’s a good idea to avoid acidifying foods when taking Phentermine.

Aside from acidifying foods, it’s also important to avoid unhealthy foods like sugars, simple carbs, trans-fats, junks, alcohols, and more while you’re on phentermine.

Also, there are quite some healthy foods to avoid as well. More on this later.

What are the effects of these foods on your body, and why are they important to avoid if you’re on phentermine?

What other specific foods from each group should you avoid?

We researched each food item to help you stay informed.

Continue reading to learn more about each one so you can make the right food choices.

7 Types Of Foods to Avoid While Taking Phentermine

Phentermine is an FDA-approved obesity drug designed to help you lose weight through appetite suppression.

However, it’s only ideal for short-term use, usually, just a maximum of 12 weeks, because it has the potential to become addictive and could cause more severe withdrawal symptoms the longer you use it.

That’s why it’s important for you to make the most of this drug while you’re using it.

As an appetite suppressant, it’s likely to help crush your cravings, but you can also boost its effects by choosing the right kinds of foods to eat and avoid.

Keep the following food groups in mind and avoid them at all costs:

1. Acidifying Foods

We put acidifying foods high up on the list because they can have a potent effect on your body, and can directly affect how phentermine is metabolized and excreted.

Studies show that these acidifying foods can make you excrete phentermine at a much faster rate compared with alkalizing foods. The shorter time that phentermine stays in your body, the lower its effects.

It makes sense, therefore, to pick the ones that keep phentermine stay much longer.

Plus, these acidifying foods can inhibit your body’s fat-burning processes, possibly making you gain weight. So, they’re really counterproductive foods when you’re trying to lose weight with this prescription drug.

Take note of the following acidifying drinks and foods to avoid while you’re taking phentermine:

  • Soda of all types and flavors
  • Coffee and caffeine-containing foods or workout supplements (such as pre-workouts)
  • Ice cream
  • Sugars
  • Alcohol
  • Butter
  • Food products with white flour, such as bread and pastries

2. Sugar

You might have noticed that a lot of unhealthy foods are also too sweet.

Diabetics sugar

Sugar makes donuts, soda, processed fruit juices, ice cream, and other tempting foods so delicious that our brains are often wired to crave these tasty treats.

Sugar-rich foods don’t really interact with phentermine to cause dangerous side effects.

However, if you can’t curb your cravings and continue to eat these delicious, sugary foods, then you’re actually undermining your weight-loss efforts. It would be like you’re simply drinking phentermine for nothing.

Always remember that your body considers sugars as fuel – but anything in excess gets stored as fats. It’s your body’s way of stockpiling fuel for future use. It’s a survival mechanism.

But the more fats your body stores, the harder it is to lose weight.

Ask yourself if it’s really worth stockpiling those sweets as fuel. It’s really not.

Remember that you’re taking phentermine to lose weight, so it’s really best to avoid foods that directly increase your chances of gaining weight.

Aside from fat storage, sugars can also increase your risks for obesity and other medical issues, including diabetes and elevated insulin resistance.

So, take note of these sugary foods and avoid them while taking phentermine (and even after you’re done with your treatment plan):

  • Store-bought, packaged fruit juices
  • Candies
  • Dried fruits
  • Frozen meals
  • Processed meals

Of course, there are also lots of foods that are naturally high in sugar, particularly sweet fruits like mangoes, pomegranates, and cherries. But they’re also rich in vitamins and minerals, which can be healthy for you, so these aren’t included in the foods you need to avoid.

It’s the bad sugar levels in the processed foods listed above that are unhealthy and unnaturally high.

3. Refined & Simple Carbs

Refined sugar isn’t the only sweet thing to avoid. Lots of simple carbohydrates can also increase your fat stores and bring your blood sugar to unhealthy levels.

Some of the foods with simple carbs that you should avoid while you’re taking phentermine and trying to lose weight:

  • Candies
  • Chocolate
  • Jam
  • Products with white flour (such as white bread or cakes of any form)
  • Cookies, biscuits, and crackers
  • Soda
  • Flour tortillas
  • Pasta
  • Packaged cereals

4. Sugar Substitutes (Like Agave)

Most people have this mistaken notion that because sugar is bad, then sugar substitutes are good because they aren’t sugar. Well, that’s not entirely true.

Sugar substitutes like agave can actually be bad for your health.

Although marketed as a ‘natural’ sweetener because it comes from extracts of the cactus plant, agave can actually increase your sweet cravings. That means that it could easily work against the effects of phentermine’s appetite suppression.

Agave doesn’t have the same components as regular sugar, but it’s high in fructose and is also a highly refined product. Choosing agave over sugar is really making a similar bad choice.

Plus, it also follows a similar manufacturing process to HFCS (high fructose corn syrup), an unhealthy sweetener linked to cardiovascular disease, obesity, diabetes, and non-alcoholic fatty liver disease.

Considering that phentermine can increase your risks for cardiovascular disease, you certainly should avoid something that also has a similar effect on the heart.

5. Processed Meats & Junk Foods

There are so many unhealthy things going on with junk foods and processed meats that it’s a wonder they’re still being sold to this day!

These unhealthy foods contain highly processed oils, empty calories, and a lot of salt that can make you gain weight. They also increase your risk of obesity.

Like the foods above, they’re counterproductive to your phentermine use.

They’re easy to find, but avoid these unhealthy foods as much as possible:

  • Salted potato chips and french fries
  • Any kind of junk food or chips
  • Fast food meals
  • Processed meats (e.g., canned meat, salami, sausages, bacon, corned beef, etc.)

6. Foods With Trans-Fats

Foods with trans-fats are bad because they can increase your risk of heart disease.

Again, remember that phentermine can also cause heart problems. Mixing it with foods that also cause heart issues can greatly increase your risk of developing heart disease. They can even increase your risk of a heart attack.

So, avoid foods containing trans-fats, whether you’re on phentermine or even on a regular diet:

  • Vegetable oils
  • Margarine

7. Alcohol

Thinking of grabbing a pint of beer or a glass of wine to reward yourself after a busy day? Hold that thought off if you’re taking phentermine.

It is dangerous to combine alcohol and phentermine. The combination can be so potent that it could lead to chest pains, elevated blood pressure, and, in the worst cases, even death.

But even if you manage to side-step these dangerous effects, it’s really not a good idea to combine the two.

Alcohol contains a lot of empty calories and high amounts of sugar that could make you gain weight and also affect your liver.

Your liver houses your body’s fat-burning systems, but the combination of phentermine and alcohol can inhibit this process for several days. It could lead to a reduced chance of burning fats.

The prolonged effect could make you lose muscle mass instead of fats when you go on a diet or workout.

Healthy Foods to Avoid While Taking Phentermine

When you’re trying to lose weight, the first thing that comes to mind is eating healthy foods, right? Sadly, not all healthy foods are ideal for you, especially if you’re trying to lose weight while using phentermine.

Some of these foods are also promoted as ‘healthy’ on social media via scrumptious Instagram-perfect posts.

In reality, however, they can be bad for you.

It’s always a good idea to ask your dietician or coach if they can recommend a diet plan that works for you, particularly if you have an underlying medical condition or other situations that could be affected (or worsened) by certain foods.

Let’s take a look at some of the healthy foods that you might need to avoid while taking phentermine:

1. Soy Milk

Marketed as a healthy, vegan alternative to dairy-based milk, soy milk is believed to be a good choice, particularly if you have dairy allergies.

However, soy milk is rich in natural phytoestrogens, which are estrogen hormones that occur in plants. These plant-based hormones can mimic estrogen in your body.

Increased estrogens in your body can affect its natural balance and could wreak havoc to your system, especially if you have hormone conditions like PCOS (polycystic ovary syndrome) or a thyroid problem, such as hypothyroidism or hyperthyroidism.

Now, most phentermine users have weight issues, with many due to thyroid problems or other hormonal imbalances.

So, it’s important to stay away from foods that contain hormones or hormone-like properties.

Some people who chose soy milk as a substitute for dairy discovered that it can also cause similar symptoms to dairy-induced digestive issues, including:

  • Bloating
  • Fluid retention
  • Tummy discomfort

2. Kale & Other Cruciferous Vegetables

Kale and most cruciferous vegetables are highly nutritious foods, but they’re also considered goitrogenic foods. This means that they contain goitrogens such as thiocyanate, which are substances that can contribute to an enlarged thyroid.

Many people with obesity might have a thyroid problem, diagnosed or undiagnosed. With so many people taking phentermine to lose weight due to an obesity issue, it’s really best to simply avoid these foods.

Aside from kale, take note of these cruciferous vegetables to avoid:

  • Arugula
  • Broccoli
  • Cabbage
  • Cauliflower
  • Brussel sprouts
  • Collard greens
  • Mustard greens
  • Bok choy
  • Watercress
  • Turnips

They remain healthy food options, especially if consumed in small quantities. However, it’s best to ask your doctor before eating any of these foods.

Experts also advise against juicing kale because that might concentrate the vegetable’s components.

3. Canned & Processed Soups

Canned or processed soups are often marketed as healthy, nutritious foods for busy folks who prefer the convenience of getting them to making soup from scratch.

However, like processed meats and junk foods, these can also contain a lot of salt, stabilizers, and other additives that prolong their shelf life.

These unhealthy foods can undermine your progress with phentermine. Don’t believe the ads because these foods are really unhealthy.

4. Granola

They’re a favorite breakfast or to-go snack item, but granola can be packed with unhealthy levels of sugar and could contain highly processed oils or trans-fats.

Although the nuts, oats, and other ingredients might seem healthy, granola as a whole can be unhealthy. It’s best to avoid this food if you’re on phentermine.

5. Sushi

This Japanese food is yummy, but remember that they are made mostly of white rice. Aside from having high carb levels, the small bites can make it easy for you to eat more than you normally would.

White rice has a very low nutrition value, and some of the sauces added to sushi can increase your body’s acidity levels.

As a potentially acidifying food, it’s best to avoid sushi or risk losing phentermine’s effectiveness more quickly.

Healthy Foods To Eat With Phentermine

So, which foods should you eat with phentermine?

You’d certainly want to focus on alkalizing foods, which can maximize phentermine’s effects in your body by keeping it in your system for a longer time.

Examples of these alkalizing foods can include:

  • Bananas
  • Apples
  • Almonds
  • Chestnuts
  • Grapes
  • Carrots
  • Cucumbers

The above list is also a good idea because most fruits and vegetables are rich sources of fiber and have high water content. Foods with more fiber and water make you feel full easily, so they perfectly match phentermine’s appetite suppression effects.

It’s also a good idea to choose healthy food options with lots of protein-rich foods while you’re on this obesity drug. These foods ensure that you continue to build muscles, making your body focus on fat-burning.

Plus, proteins take more work to metabolize, so your body will burn more calories to process them.

Phentermine intake is often limited to just a few weeks to avoid serious side effects, so it’s important to make each day count.

You can bookmark our lists of the best foods to eat and those to avoid while you’re taking this prescription obesity drug.

But you might also be wondering whether it’s possible to choose meal replacement shakes instead of a full meal while taking phentermine.

Let’s dive into that combination below.

Meal Replacement Shake To Try With Phentermine

Meal replacement shakes are quite popular among dieters because these products are so easy to prepare, generally have low calories, and can replace your meals around once or twice a day.

Because they can also make you feel full and provide you with your nutrition needs even with the low calories, it’s easy to see why they’re so popular.

But are they safe and effective to use with phentermine?

The answer is actually yes!

A 2016 study comparing the effects of using just a meal replacement shake versus a combination of shake and phentermine showed that both can significantly reduce the user’s body weight and food cravings.

However, those who used a combination of shake and phentermine lost 12.1% of their baseline body weight compared to just 8.8% lost by those on the meal replacement shake alone.

That means that the combination is effective.

If you’re looking for a good product to try, we recommend PhenQ Complete Meal Shake.

This delicious shake comes in three delicious flavors that make meals so yummy but without the extra calories: vanilla ice cream, chocolate brownie, and strawberries & cream.

PhenQ shakes flavours

Designed to replace one full meal, this shake contains as much as 16 g of whey protein concentrate, plus thirteen vegan vitamins and minerals.

It also has DigeZyme, a patented gut-boosting ingredient that contains digestive enzymes to improve digestion and support a healthy happy gut while also helping break down fats, carbs, and proteins.

This delicious and effective formulation can boost energy and control cravings to help you shed off those excess pounds naturally.

And while we’re on the subject of replacements, you might also consider replacing phentermine with a safer, healthier alternative.

Continue reading to learn about this safer phentermine alternative.

A Safe Diet Pill To Try (better than Phentermine)

Phentermine might be effective, but it’s also hounded with so many issues, particularly because it has been linked to dangerous conditions like heart failure, high blood pressure, and stroke.

You can avoid the foods we listed above to reduce your health risks, yet the healthiest option, really, is to quit taking this scheduled drug.

Instead, we recommend PhenQ, a natural dietary supplement that works similarly to phentermine in appetite suppression but without the dangerous risks.

PhenQ isn’t addictive and doesn’t require a prescription, so you can take it for as long as you want or need to.

This isn’t just an appetite suppressant. It can actually help your body burn fats and improve your metabolism, something that phentermine doesn’t do.

Also, it boosts your mood, creating an opposite effect as phentermine which is known to cause depression, anxiety, and other mood disorders in some users.

Final Thoughts

If you are taking phentermine, it is important to avoid certain foods. Sugars, simple carbs, trans-fats, junk food, and alcohol can all inhibit the effectiveness of phentermine and make it harder for you to lose weight.

Soy milk should also be avoided because it contains phytoestrogens which can interfere with the way phentermine works.

Cruciferous vegetables like kale, broccoli, and cauliflower should also be avoided because they contain goitrogens which can interfere with thyroid function.

By avoiding these foods, you will help ensure that phentermine works effectively for you and helps you lose weight quickly.

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