Written by Melanie Brown BSc (Hons), MSc. Reviewed by Dr Phoebe Howells. (December 2025).

Melanie Brown, BSc (Hons) MSc, has been a nutritionist in the area of fertility and pregnancy for 20 years. She has a master’s degree in Nutritional Medicine, and a special interest in male infertility, endometriosis, PCOS and low ovarian reserve. She covers all aspects of fertility from IVF, advising on diet and lifestyle from pre-conception through to egg collection and embryo transfer, and then beyond to pregnancy. And she is not a hard-core nutritionist; she says, “I love potatoes, wine, croissants and cake, but I think I know how to keep myself in check!” Her own experience of infertility, miscarriage and then early menopause at the age of 42, and her specialised knowledge of how IVF works, drug and nutrient interactions and a genuine empathy with her clients, gives her a unique ability to help her clients achieve their goal of having a baby. 

How weight can influence fertility outcomes. 

In UK guidance, adults are encouraged to keep waist less than half their height. In England, 29% of adults live with obesity and 64% are overweight or living with obesity, so this issue is widespread. 

Excess body fat, especially around the waist, is associated with insulin resistance, hormonal imbalances and inflammation; all of which negatively impact fertility. Evidence shows that obesity impacts the fertility of both men and women, being associated with a longer time to conception and higher chances of miscarriage and pregnancy complications. 

For example, a systematic review and meta-analysis of 21 studies found that female obesity (BMI greater than or equal to 30) was associated with significantly lower live birth rate following IVF compared to women of a BMI between 18.5 and 24.9. This also extends to men, with a meta-analysis of 50 studies reported that obesity (BMI greater than or equal to 30) was associated with an average reduction in all semen parameters in comparison with men with BMI less than 25.

What are GLP-1 Agonists?

GLP-1 agonist medications are effective tools for weight loss, which can be particularly beneficial for improving fertility for the right people, where weight is affecting your eligibility for IVF, or ability to become pregnant. Even though most of the emphasis is on a woman’s weight, male obesity is increasingly being linked with infertility, high DNA fragmentation and pregnancy complications for their female partner such as recurrent miscarriage and pre-eclampsia. So, they can be an incredibly effective tool to help people struggling with weight loss.

However, as these drugs significantly reduce appetite, and cause side effects like nausea and constipation, it is all too easy to skip breakfast, grab a bag of crisps for lunch and eat a half a diet ready meal for dinner. And yes, you will lose weight but at a considerable cost to your health. Everything from energy and focus, bone health, and your immune system to your hair, skin and nails, will be affected. And of course, that means your eggs or sperm will suffer too.

Please note: the NHS recommends that you do not try to get pregnant while taking GLP-1 medications, and that you have a ‘wash out’ period of 2 months prior to starting trying to get pregnant (so, you stop taking this for at least 2 months before you start trying to conceive). This is because the effects of these medications during this time are not yet known. For more information please visit the NHS site here. 

Core Principle: Nutrient Density Over Volume

Your goal is to eat smaller, more frequent meals packed with nutrition. Do not skip meals, as this can lead to nutrient deficiencies and is not recommended for reproductive health. Think of your meals as a miniature, well-balanced version of a standard healthy plate (see below). You have to plan for being on these drugs.

Managing Common Side Effects

Nausea: This is common initially. It's important to remember you are not ill and still need to eat. Opt for smaller, nutrient-dense meals and snacks rather than trying to eat a full meal.

Constipation: Reduced food and fibre intake can lead to constipation. To manage this:

• Ensure adequate fluid intake, because often thirst is also reduced.

• Consider supplementing with psyllium husks (a couple of teaspoons in water, followed by a second glass of water) to increase fibre and try to always have some vegetables and fats as well.
  
  

Building Your Nutrient-Dense Plate

Plan your meals objectively to ensure they are balanced. For each meal, ask yourself:

Where is my protein? 

Protein is an essential component of all of your cells. This goes beyond being important for egg and sperm cells, including immune cells, red blood cells, muscle cells and everything that makes you, you. Maintaining protein intake is absolutely essential to preserve lean muscle. 

Good sources include: eggs, fish, chicken, meat, beans, lentils, chickpeas, nuts, seeds, milk, yoghurt and cheese and tofu.

If you are exercising, particularly strength training, consider adding a scoop of good quality protein powder to a smoothie or breakfast to meet increased needs without adding excessive volume. What makes a good protein powder? Less is more here; try to choose options that avoid lots of flavourings and additives. If in doubt, the less ingredients on the back of the pack, the better. 

Where are my healthy fats? 

Fats are vital for hormone production and the health of your joints, skin, hair, gut and mood. Do not opt for "low-fat" or "fat-free" products solely because of the calories, the key here is moderation.

Include sources like: avocado, nuts, and good quality olive oil. Full fat yoghurt, a slice of cheddar cheese, a sprinkle of sunflower and pumpkin seeds over breakfast or a salad and a drizzle of olive oil over salad, soup, and cooked vegetables.

Where is my whole-grain carbohydrate? 

These provide energy, B-vitamins and crucial fibre, which helps with digestion. Where people tend to make mistakes here are, the type of carbohydrate they are selecting and how much of it they include.  

Choose small portions (one or two dessert spoons) of: oats, wholemeal bread, brown pasta, or brown, black, or red rice. 

Where are my fruits and vegetables? 

These provide essential fibre, antioxidants, vitamins, and minerals. Ensure they are a part of every meal. Fibre-rich diets (wholegrains, legumes, vegetables, fruit) improve insulin sensitivity, reduce systemic inflammation, and promote a favourable gut microbiome, all factors that indirectly support reproductive health. 

In the UK, adults are advised to consume 30 g of fibre per day from a variety of plant foods. However, average intakes remain well below this level. Some fruits with high fibre per portion are berries and pears, while vegetables such as broccoli and Brussels sprouts are also particularly high in fibre.

Where are my fluids? 

Sometimes, GLP-1 agonist medications reduce both thirst and hunger, but it is vital to remember to stay hydrated. Dehydration contributes to constipation and headaches. Keep a bottle of water in your bag and a big jug on your desk. Set your phone to remind you to drink every few hours.

Essential Supplementation

Due to reduced food intake, you are at a higher risk of nutrient deficiencies (e.g., iron, B12, zinc, vitamin C). The following supplements are strongly recommended:

• A broad-spectrum multivitamin and mineral tablet.

• Omega-three fatty acids (e.g., a high-quality fish oil).

• Vitamin D: 1000 IU daily (a spray is a convenient option).

• Iron: This is particularly important for menstruating women to replenish iron lost during their period.

Key Takeaways

• Weight is something that needs to be considered when approaching fertility. This is due to the impact it can have on the health of both the egg and the sperm, as well as pregnancy complications later on. 

• Remember, these medications are designed to reduce hunger, not to stop you from eating. Your focus must shift to providing your body with the high-quality nutrition it needs to thrive, especially when you are trying for a baby. 

• GLP-1 agonist medications can be a useful tool for helping people struggling with weight loss, and in turn with fertility. However, it is important that you do not try to conceive until after the ‘wash-out’ period of these medications, as effects are not yet fully understood.