Do Weight Loss Pills Actually Work?

Article Summary:

• Certain types of weight loss pills are currently licensed to support weight loss and weight management in Canada, subject to eligibility.
• Clinical trials have shown that certain types of weight loss pills may support weight loss and weight management in individuals who meet certain thresholds. However, any weight loss or weight management treatment should be coupled with positive lifestyle changes. These include increased movement and a balanced, varied diet.
• Like any prescription weight loss or weight management treatment, weight loss pills must only be used under the guidance of a registered healthcare professional.

Do Weight Loss Pills Actually Work?

If you're considering weight loss treatment, you may be wondering whether weight loss pills are right for you. How common are side effects? How long will it take to see results? And how might treatment affect day-to-day life?

It can be difficult to provide general answers to these questions, because the answer may vary from person to person. From your starting body weight to your hormone levels, there are so many variables that can affect the ways in which your body may interact with weight management and weight loss medication.

However, we can help to set and manage expectations around treatment. In this article we'll guide you through what to expect from oral weight loss medication, and help you to decide whether this treatment may be right for you.

Who is eligible for weight loss pill treatment?

There are a few types of prescription oral weight loss medication available in Canada. [1] However each is subject to strict eligibility rules, meaning that you have to meet specific criteria to be prescribed them.

This eligibility comes down to several factors, including your body mass index (BMI) and whether you live with any other underlying health conditions, like hypertension (high blood pressure). As with any prescription drug, weight loss pills must always be prescribed by, and taken with the approval of, a registered healthcare professional. Unregulated substances are never recommended, as it’s impossible to guarantee that they contain proper ingredients or that they’re safe for you to take.

Any medication which is prescribed for weight management should also be taken as part of a holistic program. This may include making lifestyle changes, like increasing your physical activity where possible and eating a balanced, varied diet.

Do weight loss pills have any side effects?

Like any weight loss medication, mild side effects from weight loss pills are very common. And their most reported side effects often relate to the way they work. For example, some weight loss pills that aim to block fat absorption may cause digestive problems like oily spotting and more frequent, urgent bowel movements. [2]

Fortunately, these side effects are normally short-lived. Some side effects, like bowel changes, may in fact be a positive sign that the treatment is working as intended. Once your body has adjusted to the treatment, they may ease or disappear completely. [2]

For certain types of weight loss pills, these digestive side effects can be minimized by eating a low-fat diet. [2] This could mean switching to non-fat (skim) milk, or prioritizing lean proteins like chicken breast and white fish over fattier cuts of meat. Making this switch may help to prevent some of the more uncomfortable digestive side effects associated with certain weight loss medications, and support you in reaching your goals.

It's also important to be aware of the less common, but more severe potential side effects of certain types of weight loss pills. These may include pancreatitis (inflammation of the pancreas), kidney problems and, if you have type 2 diabetes, you may experience symptoms of hypoglycemia (low blood sugar). [2]

For more information on the potential side effects of weight loss pills, speak to your healthcare provider or check the specific treatment's patient medication information (PMI) leaflet.

How effective are weight loss pills?

Several clinical trials and studies have shown that weight loss pills may be effective for weight loss and weight management in individuals who meet certain BMI thresholds. [3] [4] [5] [6]

However, the effectiveness of any weight loss medication will vary from person to person. For example, a person with a higher starting body weight is likely to lose more weight during a treatment program. [7]

Weight loss medications are designed to be part of a wider, more holistic weight loss program, and so you should complement your course of treatment with positive lifestyle changes. Health Canada recommends at least 2.5 hours a week of moderate to vigorous physical activity, broken into sessions of 10 minutes or more. [8] While this can be a good target to aim for in the long term, if you're new or returning to an exercise routine it's best to start more slowly, and with activities that you feel comfortable with.

For context, "moderate to vigorous exercise" includes any physical activity which makes your heart beat faster. You should be able to talk, but singing should be more difficult. [8] Depending on your current fitness level, you could begin with chair or seated exercises, or even increase your step count while completing household chores. Incorporating gentle strength workouts, like yoga, body weight exercises or stair climbing, may also support long-term muscle and bone strength, as well as weight management. [8] If you’re not sure what exercises are suitable for you, speak to your healthcare provider for advice.

Remember that weight loss pills are not a quick fix solution, and should never be taken with this in mind. Think of treatment as a tool to support positive long-term lifestyle changes. For more advice on how to optimize your treatment plan, speak to your healthcare provider.

What if I'm not seeing results?

While weight loss may be expected when taking weight loss pills, it's not guaranteed.

The results timeline will vary, depending on the type of weight loss medication you take and the positive lifestyle changes you make. Some medications may take 4 weeks, others up to 12 weeks before you may start to see visible results. [9] [10] However, if you have any concerns during your treatment, it's worth speaking to your healthcare provider. They may be able to provide support with your current treatment program, or suggest an alternative treatment.

How can I support my treatment?

In addition to increased physical activity and a balanced, varied diet, you may also find it helpful to take certain supplements during treatment.

For example, as we've mentioned, some weight loss pills work by reducing the amount of fat absorbed by the body. And this may lead to uncomfortable digestive adverse effects like excess gas, stomach pain and bloating. Adding soluble fibres like psyllium husk to your diet may help to ease some of these side effects, by binding the undigested fat to better regulate how often you need to have a bowel movement. [11]

Clinical trials have also shown that green tea extract can have a positive impact on weight loss. [12] And, when taken alongside certain types of oral weight loss medication, green tea may help to reduce the amount of fat your body absorbs from food you eat. [13]

However, it's always best to check with your healthcare provider before you begin any supplements while taking weight loss medication.

Which weight loss pill is right for me?

So, which weight loss pills actually work? We can point to data from clinical trials. And we can assess which medications have been proven most effective across a specific group of people. However, it’s almost impossible to determine the right treatment pathway for a specific individual without a thorough understanding of their current health and medical history.

In other words, results from oral weight loss medication will vary from person to person. This is why it's really important to complete any course of weight loss medication under the guidance of healthcare professionals. They'll be able to recommend the right treatment, assess your ongoing eligibility and monitor your progress, adjusting your treatment program if necessary.

To increase your chances of reaching your treatment goals, build a consistent dosage plan (as with any medication, consistency is key in treatment), and also try to establish sustainable lifestyle changes. These may include increased movement and physical activity, eating a balanced, varied diet and aiming for 7-9 hours of sleep each night.

Over time, these small changes may develop into lasting, healthy habits that support your ongoing weight management achievements long beyond your final treatment dose.

Find out what treatment is suitable for you with MedExpress.

References

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2. Canada,. Drug Details - Drug and Health Product Register [Internet]. Hres.ca. 2017 [cited 2026 May 8]. Available from: https://hpr-rps.hres.ca/details.php?drugproductid=1501&query=%2A
3. Nih.gov. 2024 [cited 2026 May 8]. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC5633321/
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