Tag: One Meal A Day

Does Meal Timing Affect Your Metabolism and Health?

On By Dr. Scott RennieIn Weight Loss & Metabolic HealthLeave a comment

When you eat can matter as much as what you eat. Not a fad, a measurable physiological pattern, and one most people never think to adjust. Timing affects weight management, metabolic health, and even the risk of chronic disease, and the field studying the connection between circadian rhythms and eating patterns has a name: chrononutrition.

Typical eating habits in the U.S. don’t line up well with what the research suggests is healthiest. Most people eat less than a quarter of their daily calories before noon, and more than a third after 6 p.m. The average eating window stretches nearly fifteen hours a day (Gill and Panda, 2015). That long, backloaded pattern is linked to higher body fat, worse glucose tolerance, and poorer metabolic outcomes.

Evidence favors eating earlier. In one trial, people who made breakfast their largest meal had better glucose and insulin control, felt more satisfied during the day, and lost more weight than those who made dinner the main meal (Jakubowicz et al., 2013). That tracks with circadian biology: the body handles nutrients more efficiently in the morning than late at night.

Breakfast does more than supply calories. Regular breakfast eaters tend to take in more vitamins and minerals overall (St-Onge et al., 2017), and they show lower rates of obesity and more stable weight over time. Skipping breakfast, by contrast, tracks with higher BMI, larger blood sugar swings, and greater cardiovascular risk.

Time-restricted eating fits the same pattern. Narrow the eating window to eight or twelve hours and total calorie intake often falls on its own, insulin sensitivity improves, and fat oxidation increases (Gill and Panda, 2015). Early time-restricted eating, where meals cluster in the morning and early afternoon, improves appetite control and fat metabolism specifically (Ravussin et al., 2019).

Intermittent fasting runs on the same logic. The most common version is 16:8: fast sixteen hours, eat during an eight-hour window. Alternate-day fasting has also been studied, and it produces weight loss similar to plain calorie restriction, though dropout rates run higher (Trepanowski et al., 2017).

What the science of chrononutrition shows is that timing matters. Shifting more calories to the first part of the day improves metabolism and weight control, breakfast and early meals set the body up for better glucose regulation and satiety, and time-restricted eating and intermittent fasting add tools on top of that, especially when they lean toward earlier eating windows rather than later ones. For patients, these strategies are often more about changing the clock than drastically changing the plate.

Scott Rennie, D.O.
Board Certified in Obesity Medicine and Family Medicine

This blog is for educational purposes only and does not constitute individual medical advice. Always consult your own physician before making changes to your health, medications, or treatment plan.

References:

  • Gill S, Panda S. A Smartphone App Reveals Erratic Diurnal Eating Patterns in Humans that Can Be Modulated for Health Benefits. Cell Metabolism. 2015;22(5):789-798. PMID 26411343. https://pubmed.ncbi.nlm.nih.gov/26411343/
  • Jakubowicz D, et al. High Caloric Intake at Breakfast vs. Dinner Differentially Influences Weight Loss of Overweight and Obese Women. Obesity (Silver Spring). 2013;21(12):2504-2512. PMID 23512957. https://pubmed.ncbi.nlm.nih.gov/23512957/
  • St-Onge MP, et al. Meal Timing and Frequency: Implications for Cardiovascular Disease Prevention. Circulation. 2017;135:e96-e121. PMID 28137935. https://pubmed.ncbi.nlm.nih.gov/28137935/
  • Ravussin E, et al. Early Time-Restricted Feeding Reduces Appetite and Increases Fat Oxidation But Does Not Affect Energy Expenditure in Humans. Obesity (Silver Spring). 2019;27(8):1244-1254. PMID 31339000. https://pubmed.ncbi.nlm.nih.gov/31339000/
  • Trepanowski JF, et al. Effect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults. JAMA Intern Med. 2017;177(7):930-938. PMID 28459931. https://pubmed.ncbi.nlm.nih.gov/28459931/

Can You Do Intermittent Fasting on Ozempic or Wegovy?

On By Dr. Scott RennieIn Weight Loss & Metabolic HealthLeave a comment

Weight comes up in almost every visit I do. For some patients it is fifteen pounds standing between them and a better blood pressure number. For others it is obesity that has already done damage, and the conversation starts further back. The work can feel overwhelming from the inside. What’s changed is that the tools finally match the size of the problem. Medications like Ozempic, Wegovy, Mounjaro, and Zepbound, the GLP-1 receptor agonists, have shifted how this is approached, and paired with a structure like intermittent fasting they help people lose weight and keep it off.

What GLP-1 Agonists Do

These drugs mimic glucagon-like peptide-1, a hormone that regulates appetite and blood sugar. Given as medication, they slow gastric emptying and push stronger satiety signals to the brain, so fullness arrives earlier and stays longer. They also improve insulin sensitivity, which is why they earned their place in type 2 diabetes first.

The weight effect is substantial. Wegovy and Zepbound carry FDA approval specifically for weight loss. Ozempic and Mounjaro are approved for diabetes and produce strong weight results as well, which is the source of most of the confusion patients arrive with about which drug is which.

How They Work With Intermittent Fasting

Intermittent fasting improves insulin sensitivity, supports fat loss, and helps regulate hunger hormones. Staying with it is the hard part. Many patients tell me they can’t get past the hunger. GLP-1 medications change that equation by blunting appetite and cravings, which makes a fasting schedule something a person can actually hold.

A patient of mine started a 16:8 fasting plan (16 hours fasting, 8 hours eating) while on a GLP-1 medication. Before starting the medication, she felt shaky and irritable during fasting. After starting, she was surprised by how manageable it felt. She ate smaller meals, felt full, and didn’t struggle to maintain the fasting window.

Side Effects and Adjustments

Nausea leads the list, and it’s worst early. Diarrhea and reflux show up too. Most of it settles as the body adapts. Start low, titrate slowly, and resist the urge to chase the next dose because the scale stalled for two weeks. Patients who stay in contact through the titration get their dose adjusted before they quit over side effects, and the ones who go quiet are the ones who stop the drug entirely.

Barriers to Access

Getting these medications is its own project. Cost is the main wall. Insurance coverage for weight loss remains inconsistent in a way that’s hard to explain to a patient who has just been told the drug would help, and out-of-pocket pricing is punishing. Demand has outrun supply, so delays and shortages are part of the picture.

Then there are the compounded versions. Some pharmacies sell them well below brand pricing, and they’re not FDA-approved. Safety and potency can’t be guaranteed. I tell patients to stay away from them, and I don’t soften that advice when someone pushes back on price.

Putting It Into Context

These aren’t quick fixes. They are tools, and they work when they sit on top of durable changes: balanced eating, regular activity, attention to mental health. Intermittent fasting is one workable way to structure eating alongside them. The lifestyle piece doesn’t become optional because a medication is doing part of the lifting.

When patients pair the medication with habits they can sustain, results hold longer and vary less. The goal is a set of strategies that still works three years from now, not the fastest possible drop on the scale.

Scott Rennie, D.O.

Sources

U.S. Food and Drug Administration. FDA Approvals: Wegovy, Zepbound.

Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity. N Engl J Med. 2021;384:989-1002.

Jastreboff AM, et al. Tirzepatide Once Weekly for the Treatment of Obesity. N Engl J Med. 2022;387:205-216.

American Diabetes Association. Pharmacologic Approaches to Glycemic Treatment: Standards of Medical Care in Diabetes, 2024. Diabetes Care. 2024;47(Suppl 1):S181-S202.

Board Certified in Obesity Medicine and Family Medicine

This blog is for educational purposes only and does not constitute individual medical advice. Always consult your own physician before making changes to your health, medications, or treatment plan.