What GLP-1 Medications ACTUALLY Do, and Why Nutrition Still Matters

GLP-1 receptor agonists have changed the conversation around weight management in South Africa. Ozempic, Wegovy and Mounjaro have all become household names lately (although Saxenda has been available as a daily injection for some time). Whatever the brand, the questions I hear in my practice are the same: what should I be eating, and why do I still need a dietitian if the medication is doing the work?

What the medication does
GLP-1 is a hormone your gut releases after eating. It slows the rate at which your stomach empties, prompts insulin release when blood glucose rises, and signals fullness to the brain. These medications mimic that hormone at much higher levels than your body would produce on its own.
The practical effect is that you feel full sooner, stay full longer, and think about food far less. Many patients describe a striking quiet where constant food preoccupation used to be. Appetite drops, portions shrink, and weight comes off.
What the medication does not do
It does not decide what you eat. It does not protect your muscle mass. It does not supply protein, calcium, iron, or fibre. It does not teach you how to eat when you eventually come off it.
The medication creates a situation that is nutritionally unusual. You are eating substantially less food than before while your body's requirements for protein, vitamins, and minerals have not dropped at all. A smaller volume of food has to carry the same nutritional load. That only happens by design, not by accident.
Where things go wrong
The problems I see most often in practice fall into a few patterns:
Eating far too little. Some patients drop to under 500 calories' worth of food a day without realising it, simply because they are not hungry. Fatigue, hair thinning, dizziness, and poor concentration follow.
Losing muscle along with fat. Rapid weight loss without adequate protein and resistance training means a meaningful proportion of what you lose is lean tissue. This lowers your metabolic rate and makes regain more likely later.
Eating whatever goes down easily. When appetite is low, people gravitate toward soft, sweet, easy foods. Tea and a rusk. A smoothie. A slice of toast. These are the least nutrient-dense options available.
Constipation. Along with choosing easy, quick food options, many people land up eating very little fibre-rich foods (e.g. brown rice, quinoa, bran).
Never learning new habits. If nothing changes except appetite, then when the medication stops, so does the weight loss.
The nutrition brief while on a GLP-1
Think of your reduced appetite as a limited budget. Every meal has to earn its place. That means:

• Protein at every meal, without exception
• Vegetables and fruit for fibre, potassium, and micronutrients
• Enough total food to meet your needs, even on days when you are not hungry
• Adequate fluid, which is easy to neglect when you are not thirsty
• Structured eating times rather than waiting for hunger to arrive

The long view
Obesity is a chronic condition, and these medications are chronic treatments. Some people will stay on them long term. Others will stop, whether by choice, because of cost, or because of side effects. The nutritional work you do now determines what happens in either scenario. If you build a way of eating that you can sustain, the medication becomes a tool that supported a change rather than the change itself.
Over the next nine posts I will work through protein targets, side effect management, micronutrients, social eating, and what to do if and when you come off.

If you would like a plan built around your bloods, your medication, and your actual life, my practice in Illovo Johannesburg sees patients in person and online.