Weight-loss injections: lean mass, training, side effects and questions for your doctor

Weight-loss injections, medications that reduce appetite, change hunger, portion sizes and the way the body responds to training. This guide brings together what studies show about lean mass, training, side effects and protein, with logs and questions to bring to your appointment. It does not recommend any medication, dose, start or stop of treatment: these medications require medical follow-up.

Lean mass: 6 questions for your next appointment

In a large study with these medications, 38% of the weight lost was counted as lean mass and 62% as fat. Since muscle makes up about half of lean mass, 4 scientific societies estimate about 20% muscle in the weight lost, a calculation rather than a direct measurement [1]. Lean mass also includes organs, fluids and the water in fat tissue [2].

Strength training changes that result. In older adults with obesity, without these medications, weight loss was the same in the exercise groups, but lean mass fell 5% with aerobic training alone and 2% with strength training [3]. Protein helps, but without strength training it is probably not enough [1]. A study of 232 adults will test training and protein alongside the medication, with no results yet [4].

• Did my scan measure muscle or lean mass? Which method was used?
• Is the change on my scan larger than expected for the change in my weight?
• Should my strength be measured too? Which test makes sense for me?
• How much protein per day makes sense in my case, and based on which weight?
• What should I do on days when I am not hungry and the protein target feels too big?
• Do I have any restrictions for strength training? Which professional should I start with?

Before changing your medication: 8 questions

Weight that comes back after stopping has more to do with the body than with willpower. In 228 adults who stopped the medication and lifestyle support after 68 weeks, about two thirds of the weight lost returned within a year [5]. In 670 adults, those switched without knowing to an injection with no drug regained 14% of their weight over 52 weeks, while those who stayed on the medication lost a further 5.5% [6].

Appetite reacts to weight loss, by about 100 kcal more per day for each kilogram lost, according to a calculation made with another type of medication [7], and even without these drugs, hunger and appetite hormones were still altered a year after a very restrictive diet [8]. A review of 37 studies estimated regain of about 0.8 kg per month after stopping the newer medications [9]. Training may leave a mark: in Copenhagen, people who did supervised training alongside an older drug were 5.1 kg lighter a year after stopping everything [10].

• In my case, is treatment intended for a set period or for the long term?
• If I ever want to change or stop, how do we plan that safely?
• What may change in my hunger, and what do I do if it rises a lot?
• Which tests and measurements should we track before and after any change?
• Do any of my health conditions change this decision?
• How much protein per day makes sense for me, and who adjusts it with me?
• Do I have any restrictions for strength training?
• How often should we meet after a change, and when should I contact you before then?

Training on a smaller plate: a 4-week log

Eating less changes what training delivers. In an analysis of strength studies, people eating less than they burned gained less lean mass with similar strength, and about 500 kcal below energy needs was enough to prevent gains [11]. In adults with overweight, strength training reduced lean mass loss by about 0.8 kg during weight loss [12].

Strength was greater with 2 or more sessions per week, heavier loads, 2 to 3 sets and the exercise done at the start of the session [13]. In a hard week, strength and muscle were maintained for up to 32 weeks with 1 session and 1 set per exercise in younger people, without reducing load; older people needed up to 2 sessions with 2 to 3 sets [14][15]. Experts recommend strength training and protein adjusted to each person’s age, health and medications [16].

A sample week, filled in:

• Also log the week’s sessions, the days training was reduced and symptoms such as nausea, dizziness or weakness.
• On a hard day, cut sets before cutting load, if you feel well.
• After 4 weeks, compare the load and reps from the first and last week.

Your stomach on these medications: suggestions by symptom

Side effects are common. In 68-week trials with 2,117 adults, 43.9% reported nausea, versus 16.1% of those receiving an injection without the drug; there was also diarrhea (29.7%), vomiting (24.5%) and constipation (24.2%). Half of nausea episodes lasted up to 8 days, and constipation episodes up to 47 days [17].

The suggestions below come from an expert consensus and were not tested one by one [18]; recent reviews say studies on diet during this treatment are still limited [19][20].

A 14-day diary helps separate chance from a pattern: write down the day and time, what and how much you ate, the symptom, its strength from 1 to 5 and how long after it appeared. At the end, mark what happened more than once; a single time is not enough to blame a food.

Counting protein: a food list and a sample day

The guidance from the 4 scientific societies cites 80 g to 120 g of protein per day as a possible target, or 1.2 g to 1.6 g per kilogram for people losing weight, with no consensus on which weight to use [1]. In a small study, 23 people who started the medication without dietitian support ate an average of 0.9 g of protein per kilogram per day [21], and in 120 adults the medication group ate about 270 kcal less at a free lunch [22].

A sample day, suggested by us and not tested in people on these medications: 2 eggs, 170 g of yogurt, 100 g of chicken, 30 g of peanuts and 100 g of tuna add up to 85 g. On low-appetite days, start your meal with the protein and choose foods that take up little space, such as fish, eggs, yogurt and cheese.

How CatLena uses it

On the Body screen, weight, body fat percentage and body composition appear in one place. In the example below, 77.3 kg with 15.0% body fat results in the Balanced profile. With measurements logged over the weeks, it is easier to bring your doctor the trend in weight together with the trend in fat, not just the number on the scale.

When to see a professional