Weight loss injection users are missing out on three vital nutrients, running the risk of hair loss, constipation, and rashes, according to recent research.
An estimated 2 million people in Britain use these injections, which mimic a natural gut hormone to signal fullness, suppress hunger, and lower appetite.
While reducing appetite helps individuals lose substantial weight, it also brings drawbacks because eating less makes consuming enough essential nutrients difficult.
A review of multiple studies conducted by the Harvard T.H. Chan School of Public Health and the University of Copenhagen revealed that GLP-1 users lack three specific nutrients.
These are:
- Vitamin B12, which helps make healthy red blood cells and protects the nervous system
- Protein, which repairs and builds muscles and other tissues
- Fibre, which helps the gut work properly and prevents constipation
"GLP-1 based therapies have transformed obesity treatment, resulting in significant weight loss and broad metabolic improvements," researchers stated.
"However, their rapid adoption has outpaced the development of adequate nutritional support systems, leaving many patients without dietary guidance despite experiencing profound reductions in appetite and food intake."
"People often drastically cut their energy consumption, risking inadequate protein intake, micronutrient deficiencies, low fibre intake, and loss of lean mass, consequences that are largely preventable with proper guidance."
Meeting basic dietary needs becomes especially difficult when individuals experience a very low appetite or when nausea complicates eating, researchers added.
Are you deficient in vitamin B12?
According to the NHS, the full list of potential signs of a B12 deficiency includes:
- Rapid breathing or shortness of breath
- Headaches
- Indigestion
- Loss of appetite
- Palpitations
- Problems with your vision
- Feeling weak or tired
- Diarrhoea
- A sore or red tongue, sometimes with mouth ulcers
- Problems with memory, understanding and judgement (cognitive changes)
- Numbness
- Muscle weakness
- Psychological problems (mild depression, anxiety, confusion, dementia)
- Problems with balance and coordination
- Pins and needles
- Incontinence
The review noted that only 43 per cent of GLP-1 users consumed enough protein, which is about 1.2 grams of protein per kilogram of body weight each day.
"Low protein intake significantly increases the risk of disproportionate lean mass loss during weight loss," researchers pointed out.
This supports earlier findings from Italian scientists published in April, who discovered that 88 per cent of GLP-1 users failed to meet protein intake guidelines.
Protein deficiency can cause conditions such as hair loss, fatigue, compromised immune systems, and osteoporosis.
This happens because insufficient protein speeds up muscle loss, which impacts balance, mobility, and long-term metabolic health.
Consequently, NHS guidelines now recommend that people on weight loss medication engage in strength training to fight the rapid loss of both muscle and fat.
The new review, published in The Journal of Nutrition, highlighted low fibre intake as a problem for weight loss injection users.
This can cause nausea, bloating, and constipation, "creating a cycle in which patients eat even less."
Most slimmers also missed dietary guidelines for other nutrients like vitamin D, potassium, magnesium, and iron, the review discovered.
One study analyzed in the review found that nutritional deficiencies appeared in 12.7 per cent of GLP-1 users within 6 months of starting treatment.
This figure increased to 22.4 per cent after 12 months of using the injections.
As a result, patients may suffer from symptoms such as fatigue, hair thinning, and ongoing gastrointestinal issues.
Researchers additionally discovered that GLP-1 users with type 2 diabetes might face a higher risk of vitamin B12 deficiencies, particularly if they take metformin.
A B12 deficiency can trigger many problems, including extreme tiredness, muscle weakness, mouth ulcers, skin changes, and rashes.
This vitamin frequently occurs in foods like meat, fish, milk, cheese, and eggs, meaning people on vegan diets face a higher risk of deficiency.
"As GLP-1 prescriptions reach millions of patients across diverse and often under-resourced clinical settings, integrating nutrition into this care model is not just advisable; it is urgent," researchers emphasized.
They stated that weight loss injection users should get guidance from dietitians and other health professionals to maintain proper levels of key nutrients and minimize treatment side effects.
The best method to ensure sufficient protein consumption is eating foods like beans, pulses, eggs, fish, and lean meat, preferably avoiding red or processed options.
However, individuals working hard at the gym can boost their protein intake using protein powder.
A 1kg bag of Impact Whey Protein Powder costs £25.99, which equals just over 50p per serving.
Similarly, the best way to get fibre is by consuming wholegrains, pulses, fruit, vegetables, nuts, and seeds.
Alternatively, shoppers can purchase High Fibre Blend capsules containing psyllium husk from Holland and Barrett for £15.99, amounting to 53p a day.
Finally, vitamin B12 capsules are available at Holland and Barrett for £6.80, which works out to just under 7p per serving.
