.svg)
The Science Behind Weight Loss: How Caloric Deficits Work
Ever stepped on the scales and wondered, "How exactly does weight loss happen?" We all know the basics: eat less, move more. But what's the science behind it? Understanding the mechanics of weight loss can empower you to make informed choices and achieve your goals sustainably. Let's delve into the fascinating world of calorie deficits and discover how they hold the key to shedding those extra pounds.
Energy Balance: The Weight Loss Equation
Imagine your body as a bank account. Calories from the food you eat are like deposits, while the energy you expend through daily activities and exercise are withdrawals. This is the fundamental principle of energy balance:
- Calories in vs. calories out. If you consistently "deposit" more calories than you "withdraw," your body stores the surplus as fat, leading to weight gain. Conversely, if you "withdraw" more than you "deposit," your body taps into its fat reserves for energy, resulting in weight loss. Source: NHS website on understanding calories
Calories: The Units of Energy
Calories are simply units of energy found in food. They fuel your body's functions, from breathing to running a marathon. These calories come primarily from three macronutrients:
- Carbohydrates: Found in foods like bread, pasta, and fruits, they provide 4 calories per gram.
- Proteins: Essential for building and repairing tissues, found in meat, fish, eggs, and beans, they also provide 4 calories per gram.
- Fats: Important for hormone production and nutrient absorption, found in oils, nuts, and avocados, they provide 9 calories per gram. Source: British Nutrition Foundation guidelines on macronutrients.
Calorie counting plays a crucial role in creating a calorie deficit. However, it's important to remember that not all calories are created equal. Prioritise nutrient-dense foods packed with vitamins and minerals over calorie-dense foods that offer little nutritional value.
Creating a Calorie Deficit: Your Path to Weight Loss
To lose weight, you need to consistently consume fewer calories than your body burns. This is where your BMR (Basal Metabolic Rate) and TDEE (Total Daily Energy Expenditure) come in. (For a detailed guide on calculating these, check out our previous blog post).
Aim for a safe and sustainable calorie deficit of 500-750 calories per day, which typically leads to a weight loss of 1-2 pounds per week. Source: NHS guidelines on safe weight loss
Here are two main approaches to achieving a calorie deficit:
- Reducing calorie intake:
- Practice portion control.
- Make healthier food swaps (e.g., choose grilled chicken over fried chicken).
- Be mindful of your eating habits and avoid emotional eating. Source: NICE guidelines on weight management
- Increasing physical activity:
- Incorporate regular exercise into your routine, including cardio and strength training.
- Find activities you enjoy to make it sustainable.
A balanced approach that combines both diet and exercise is most effective for long-term weight loss and overall health.
Your Body on a Calorie Deficit
When you're in a calorie deficit, your body needs to find alternative energy sources. This is where your stored fat comes in. Your body breaks down fat cells to release energy, leading to weight loss.
Your metabolism may also adjust slightly in response to calorie restriction. This is a natural process and doesn't mean your body is going into "starvation mode" (more on that myth later!). Source: MacLean, P. S., Bergouignan, A., Cornier, M. A., & Jackman, M. R. (2011). Biology's response to dieting: the impetus for weight regain. American journal of physiology. Regulatory, integrative and comparative physiology, 301(3), R581–R600.
Hormones like leptin and ghrelin also play a role in regulating hunger and satiety. Understanding these hormonal signals can help you manage your appetite and stay on track with your calorie deficit.
Busting Weight Loss Myths
- Starvation Mode: Contrary to popular belief, severely restricting calories doesn't cause your metabolism to shut down. While metabolic rate may decrease slightly, it's not a drastic drop that halts weight loss.
- Spot Reduction: Unfortunately, you can't target fat loss in specific areas. Doing endless crunches won't magically melt away belly fat. Weight loss happens throughout the body.
- Rapid Weight Loss is Best: While it can be tempting to aim for rapid weight loss, slow and steady wins the race. Sustainable weight loss is more likely to be maintained in the long run.
Tips for Staying on Track
- Track your calories: Use a food diary or app to monitor your intake.
- Plan your meals: Preparing meals in advance can help you stay organized and avoid impulsive food choices.
- Practise mindful eating: Pay attention to your hunger cues and avoid distractions while eating.
- Build healthy habits: Focus on making sustainable lifestyle changes that you can maintain long-term.
The Bottom Line
Understanding the science behind calorie deficits empowers you to take control of your weight loss journey. By consistently consuming fewer calories than you burn, you can achieve sustainable weight loss and improve your overall health. Remember to focus on a balanced approach, be patient with yourself, and celebrate your progress along the way!
Need more support? Check out these helpful resources:
Mounjaro is a new medication developed by Eli Lilly that contains the active ingredient tirzepatide. It was originally designed to help people with type 2 diabetes manage their blood sugar levels. Mounjaro is administered as a once-weekly injection using a self-injection pen, typically into the abdomen, thigh, or upper arm. In the UK, tirzepatide (Mounjaro) has been approved for use by the Medicines and Healthcare products Regulatory Agency (MHRA).
Besides helping with blood sugar, Mounjaro has also been found to be very effective at helping people lose weight. This is why you might have heard it called a "weight loss jab" in the media.
- How you take it: You inject Mounjaro once a week. Your doctor will usually start you on a small dose and slowly increase it over time. This helps your body get used to the medicine and can lower the chance of you feeling sick.
How it Works:
Mounjaro is like a "twin hormone" medicine. It acts like two natural gut hormones, GLP-1 and GIP. These hormones help control blood sugar and appetite.
- It helps your body release more insulin when needed and lowers sugar from your liver, improving blood sugar control.
- It makes you feel fuller sooner and for longer, helping you eat less.
- Working on both GLP-1 and GIP is thought to be why it can lead to greater weight loss than medicines that only use GLP-1 (like Semaglutide in Ozempic/Wegovy).
What is it Used For?
- Type 2 Diabetes: Mounjaro lowers blood sugar effectively, often helping patients reach better levels (lower HbA1c). It's used alongside diet and exercise, sometimes with other diabetes medicines, typically when standard treatments aren't enough, especially if weight loss would help.
- Weight Management: In studies, people using Mounjaro lost a significant amount of weight, often averaging 15-20% of their body weight over about 1 to 1.5 years. It's approved for adults with obesity (high BMI) or those with a lower BMI and a weight-related health problem.
Access in the UK:
- NHS: Mounjaro is available on the NHS for type 2 diabetes if you meet certain criteria. For weight loss, NHS access is starting gradually through specialist clinics for adults with a very high BMI and multiple weight related health issues.
- Private: You can also access Mounjaro privately through weight loss clinics, pharmacies or online services like ours if you meet the medical criteria. SheMed operates a weight management programme specifically tailored for women, which includes the potential prescription of GLP-1 medications such as Mounjaro and Wegovy, provided the individual meets their medical criteria.
Mounjaro vs. Semaglutide (Ozempic/Wegovy):
Both are effective weekly injections. Semaglutide works on GLP-1 while Mounjaro works on both GLP-1 and GIP. Studies suggest Mounjaro may lead to slightly more weight loss on average. But choice of drug depends on a number of factors and is very individual.
Side Effects and Safety:
Common side effects are usually mild stomach issues (nausea, vomiting, etc.) that often improve over time. Because it affects appetite, you'll feel less hungry. If you take other diabetes medicines, your doctor might adjust doses to prevent low blood sugar.
Serious side effects are rare, but contact a doctor immediately for severe tummy pain, persistent vomiting, allergic reactions, or worrying mood changes.
Important Note: Mounjaro works best with healthy eating and exercise. If you stop Mounjaro, appetite and weight can return if lifestyle changes aren't maintained.
Check our healthcare support page to see if Mounjaro could be a suitable option for you based on your health needs and the latest criteria.
FAQs
1. How is Mounjaro administered?
Mounjaro is given as a once-weekly injection. Your healthcare provider will guide you on the correct dosage and administration technique.
2. Can I use Mounjaro if I’m pregnant or breastfeeding?
No, tirzepatide is not recommended during pregnancy or breastfeeding, as its safety in these situations has not been established. If you are planning to conceive or are breastfeeding, discuss alternative options with your doctor.
3. How long does it take to see results with Mounjaro?
While individual results vary, many users begin noticing changes within a few weeks. Maximum benefits are typically observed after several months of consistent use, alongside dietary and lifestyle adjustments.
References
- MotherToBaby. (2024). Tirzepatide (Mounjaro®, Zepbound®) - Mother To Baby | Fact Sheets. https://www.ncbi.nlm.nih.gov/books/NBK605070/
- Watanabe, M., & Hasegawa, Y. (2021). Tirzepatide in adults with obesity and type 2 diabetes. New England Journal of Medicine, 385(11), 1046-1056. https://doi.org/10.1056/NEJMoa2107519
- Kahn, S. E., & Florez, J. C. (2023). Tirzepatide: A dual GLP-1 and GIP receptor agonist for type 2 diabetes management. PMC, 11543192. https://pmc.ncbi.nlm.nih.gov/articles/PMC11543192/
- Kahn, S. E., & Florez, J. C. (2023). Tirzepatide once weekly for the treatment of obesity. New England Journal of Medicine. https://pubmed.ncbi.nlm.nih.gov/36751934/
- Nauck, M. A., & Quast, D. R. (2020). Glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide: A review of their roles in obesity and type 2 diabetes. Endocrine Reviews, 41(3), 1-24. https://pubmed.ncbi.nlm.nih.gov/32459834/
- Kahn, S. E., & Florez, J. C. (2020). Tirzepatide: A novel dual glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1 receptor agonist for type 2 diabetes management. Endocrine Society. https://www.ncbi.nlm.nih.gov/books/NBK605070/
A groundbreaking clinical trial has revealed that Mounjaro (tirzepatide) leads to greater weight loss than its rival Wegovy (semaglutide), offering new hope for people struggling with obesity.
Head-to-Head Results: Mounjaro vs Wegovy
The study, presented at the European Congress on Obesity and published in the New England Journal of Medicine, compared the two most talked-about weight-loss injections. Over 72 weeks, participants taking Mounjaro lost an average of 20% of their body weight, compared to 14% for those on Wegovy. That’s a significant difference, especially for those with a lot of weight to lose.
Key Findings:
- 32% of Mounjaro users lost at least a quarter of their body weight, compared to 16% on Wegovy.
- Waistlines shrank more: Mounjaro users lost an average of 18cm from their waists, while Wegovy users lost 13cm.
- Health improvements: Mounjaro also led to better blood pressure, blood sugar, and cholesterol results.
- Similar side-effect profiles for both drugs.
- Women tended to lose more weight than men on both medications.
How Do These Medications Work?
Both Mounjaro and Wegovy help people feel full, reducing appetite and encouraging the body to burn stored fat. The key difference is that Wegovy mimics one appetite-control hormone, while Mounjaro targets two, which may explain its superior results.
Mounjaro and Wegovy: Availability and Eligibility in the UK
Both Mounjaro and Wegovy are available for weight management in the UK through both the NHS and private clinics. Here’s what you need to know about who can access them and how.
NHS Eligibility Criteria
Both medications are available on the NHS, but only for people who meet specific criteria:
- Adults with a BMI of 35 or above and at least one weight-related health condition (such as high blood pressure, cardiovascular disease, or osteoarthritis).
- Adults with a BMI of 30 or above who qualify for referral to a Specialist Weight Management Service (SWMS) and have not succeeded with other weight loss methods.
- Some groups, such as certain minority ethnic backgrounds or those with cardiovascular disease, may qualify with a BMI as low as 27.5.
Private Prescription Criteria
For those seeking treatment privately, the requirements are less strict:
- BMI of 30 or above, or BMI of 27 or above with a weight-related health condition or from certain ethnic backgrounds.
- Patients must complete an online or in-person consultation, including questions on weight, medical history, and current medications.
- New regulations require verification of identity and medical suitability, often with GP input or supporting records.
Estimated Monthly Costs
Customers seeking access to weight loss treatments like Mounjaro and Wegovy can conveniently receive private prescriptions through online clinics such as SheMed Healthcare. SheMed specializes in providing healthcare services tailored for women, including a dedicated weight loss programme.
Here is a breakdown of the programme's pricing:
- Starting Price: £99 for the initial dose.
- Includes: This initial cost covers a health screening, which involves a blood test to ensure the treatment is safe and appropriate.
- Subsequent Doses: Later doses are priced at £159 each.
Conclusion
This major trial confirms Mounjaro's significant edge over Wegovy, demonstrating superior weight loss and better health outcomes for individuals with obesity. Both medications represent powerful advancements in weight management and are available in the UK via NHS and private pathways, offering promising new options for those seeking effective medical treatment. If you have any questions about these medications or weight loss options, please visit the SheMed Support website for more information.