A few years ago, barely anyone outside of medical circles had heard of GLP-1 receptor agonists. Today, they are commonly used by potentially almost 10% of the general public. They work by mimicking glucagon-like peptide-1, a hormone your gut naturally releases after a meal, triggering signals of fullness, slowing digestion, and dialing down appetite in ways that have stunned even their proponents.
The result for many people is a significant and sustained reduction in daily caloric intake, often eating considerably less than before and experiencing fewer feelings of hunger between meals. For weight management, this is precisely the intended effect. But it also means that the foods and nutrients that once came from a fuller day of eating now arrive in smaller amounts.
GLP-1 is a naturally occurring incretin hormone released from intestinal L-cells in response to food. It acts on the hypothalamus (a small, almond-sized control center at the base of the brain) to promote satiety, on the vagus nerve (the primary nerve connecting your brain signal to the vital organs, like heart, lungs, and digestive tract) to slow gastric emptying.
GLP-1 receptor agonists amplify these signals, increasing the sense of fullness after smaller meals and reducing the frequency and intensity of food noise. This results in sustained reduction in daily caloric intake, which is the primary driver of the weight loss observed in clinical trials.
Fewer meals shouldn’t mean fewer nutrients, and it really emphasizes how important the nutrient density of foods and drinks is for individuals who significantly reduce their daily calorie intake through their weight-management journey.
Weight loss is rarely just fat loss. Research consistently shows that during periods of significant caloric restriction, a meaningful portion of what the body sheds is lean tissue, which includes muscle.1,2 This metabolically active muscle mass is the basis of strength, mobility, and long-term health.
Clinical evidence estimates roughly 25 to 39% of total weight lost during caloric restriction comes from lean body mass rather than fat.1,2 A 2025 meta-analysis pooling nine placebo-controlled trials (n=659) found that, across populations undergoing medically supervised weight loss (which means working with a healthcare professional and includes those on a GLP-1 journey), approximately 30% of total weight loss was lean mass.3
Foods and supplements play a role in daily caloric intake. It’s a reason to be intentional about choosing nutrient dense options with the right macro and micronutrients that provide when choosing what’s best for you.
For anyone eating less over an extended period, supporting lean muscle preservation is one of the most important things you can do for your long-term health. The encouraging news: a 2021 randomized controlled trial in the New England Journal of Medicine demonstrated that adding resistance exercise to a reduced-calorie approach effectively preserved muscle mass and bone mass that would otherwise have been lost.6 These findings suggest that changes in muscle mass during periods of calorie restriction may be influenced by factors such as exercise, nutrition, and other lifestyle habits.
Creatine is a naturally occurring compound synthesized in the body from the amino acids arginine, glycine, and methionine. Approximately 95% of the body’s creatine is stored in skeletal muscle, where it plays a central role in regenerating ATP, the cell’s primary energy currency, during high-intensity effort.
Supplemental creatine acts on muscle and performance through several well-characterized mechanisms:7,8
The evidence base for creatine is unusually deep. The most comprehensive synthesis to date, a 2024 GRADE-assessed meta-analysis of 143 randomized controlled trials, found that creatine supplementation increased body mass by 0.86 kg, increased fat-free mass by 0.82 kg, and modestly reduced body fat percentage.12
Creatine can move the needle even on its own. In a randomized trial of 30 healthy men and women, five days of creatine supplementation increased fat-free mass with no exercise program at all.13 A 2025 randomized controlled trial reported a similar result, with creatine increasing lean body mass during a training-free period, an effect that was most pronounced in women.14
Training, though, is what amplifies the effect. A 2022 systematic review of 35 trials (n=1,192) found creatine increased fat-free mass by 0.68 kg overall, rising to 1.10 kg when combined with resistance training — a 61% increase.15Similarly, a 2017 meta-analysis of 22 trials in older adults found that creatine plus resistance training added 1.37 kg of lean tissue mass over resistance training alone, along with significantly greater gains in both chest-press and leg-press strength.The benefits extend to body composition more broadly. A 2023 meta-analysis found that resistance training plus creatine reduced body fat percentage by 1.19% compared with resistance training alone in adults under 50. Taken together, the data make a strong case: creatine reliably supports lean muscle mass and healthier body composition, and pairing it with resistance training is what makes those benefits count.
When your diet changes, whether through intention, routine, or circumstance, your body’s demand for key nutrients doesn’t decrease with it. During periods of reduced food intake, nutritional gaps can widen precisely when the body needs support most.
The International Society of Sports Nutrition’s 2017 Position Stand explicitly notes that creatine supplementation during energy-restriction-induced weight loss may be an effective way to help preserve muscle mass, promote fat loss, and support healthy body composition.18 A 2024 updated consensus statement by 11 leading creatine researchers reaffirmed this position, emphasizing creatine’s role as we age and during dietary change.19
The broader principle is clear: when you’re eating less, getting the right nutritional support becomes even more important.
While there are many ways to dose creatine, the most commonly recommended evidence-backed daily protocol is 5 grams of creatine monohydrate. Full muscle saturation occurs in approximately 28 days at this amount with gastrointestinal tolerance.20
The International Society of Sports Nutrition (ISSN) recommends 3 to 5 grams per day as the standard daily maintenance dose. A 2024 updated expert consensus reaffirmed this range as effective for increasing intramuscular creatine stores, supporting lean tissue mass, and maintaining performance.*18,19
The ISSN’s 2017 Position Stand states: “Creatine monohydrate is the most effective ergogenic nutritional supplement currently available to athletes in terms of increasing high-intensity exercise capacity and lean body mass during training.” It also specifically notes that creatine supplementation during energy-restriction-induced weight loss may help preserve muscle mass.*18
Of all the well-researched supplements, creatine monohydrate has one of the most reassuring safety records in the literature. A randomized controlled trial using gold-standard kidney function testing (51Cr-EDTA clearance) found that 5 g/day had no effect on GFR, creatinine clearance, urea, electrolytes, or proteinuria, even in resistance-trained adults on high-protein diets.21 A longitudinal cohort study tracking 65 health markers in athletes over 21 months found no clinically significant adverse effects,22 and a separate study following athletes for up to five years showed no signs of renal impairment.23
One caveat worth noting: this safety data applies to people with healthy kidney function. Anyone with pre-existing chronic kidney disease should speak with their physician before use.
When you’re on a GLP-1 journey, eating less is the point. But eating less also means your body has fewer opportunities to get the vitamins, minerals, and nutrients it needs to feel its best every day. AG1 Pro is designed to help fill that gap.* With an advanced blend of vitamins and minerals to support everyday nutritional needs, AG1 Pro works alongside the progress you’re already making.*