Weight Loss Swimming with Michael Phelps

Take Home Points on Appetite and Swimmers:

  1. Cold water may stimulate brown adipose tissue, burn more energy and stimulate hunger.
  2. Stimulating brown adipose tissue could be helpful or hinder swimming weight loss, as it depends on your intensity of exercise and appetite control.
Everyone has heard the stories of Michael Phelps eating voluminous amounts of food during his training. It is hard to imagine someone can eat 10,000 calories a day and still be slim! This has made many wonder, why do swimmers eat so much?
In a recent post, the New York Times, stated:
“[b]ut swimming has a notable drawback. “It seems to stimulate appetite,” Dr. Tanaka said, more so than do vigorous land-based exercises like running. As a result, swimming is not particularly effective at promoting swimming weight loss or maintenance. In a 2005 study of exercise habits and body weight involving more than 15,000 adults ages 53 to 57, those who briskly walked, jogged or cycled gained little weight over the course of a decade. Those who swam tended to pack on pounds (Reynolds 2013).”

This article suggested swimming increases appetite and fat gain. Unfortunately, this piece does not conclude why swimming may stimulate appetite. Is it the act of swimming? Perhaps, it is the immersion? Or maybe immersion in cold water? Another thought is researched swimmers may not perform a high enough intensity to stimulate swimming weight loss for the associated appetite increase with exercise. Well, a recent study may have answered a few of these questions.

Bergamin (2013) performed a study in elderly subjects (~71  years) for 24-weeks. This study compared water-based to land-based exercise. This study found similar performance and exercise benefits between these two forms of training, but aquatic training reduced fat mass by 4% (P , 0.05), and dominant forearm fat decreased by 9.2% (P , 0.05). In addition, calf muscle density increased by 1.8% (P , 0.05).

Now, the Bergamin study is not perfect, as it did work with elderly patients in warm-water. Plus, it didn’t look at swimming, but simply in-water exercise. However, it does seem to suggest either the cold water or the motion of swimming as the stimulus for the increased swimming appetite, since warm water and exercise in water stimulate fat loss. Personally, it is likely the cold water which stimulates appetite, as brown adipose tissue

According to research I’ve read, the appetite stimulation is more a result of the body’s natural reflex to a drop in core temp. Heat is lost 25 times faster in water than air. So one is inclined to eat more relative to running or cycling. If appetite is stimulated, then why aren’t swimmers fatter?

Types of Fat

My first year in my doctoral program involved a cadaver lab. This cadaver lab was one of my favorite parts of graduate school, but at first it was a bit creepy. I’ll never forget the unveiling of our cadaver on the first day. Everyone was anxious and my lab partners and I unveiled the cadaver and the top of the head fell off (thanks Dental school)!
Over time being in the cadaver lab increased everyone’s level of comfort. At first, no one was able to eat an hour before or after the lab, but over time people become too comfortable, as some many associated body tissues with various foods. One description used between me and my lab partners was the comparison of macaroni and cheese and subcutaneous fat. The similarities between these structures were remarkable. Being able to visualize fat at this level was remarkable and left an impact on my life.
Many view fat (adipose tissue) as an enemy, but all body fat is not created equal. There are two types of fat: white (yellow, macaroni and cheese in appearance) and brown. These different types of adipose tissue have different properties and functions. Specifically, brown adipose tissue (BAT) is a good type of fat, which burns fat similar to muscle.

Types of Fat

  1. White Adipose Tissue (WAT): adipocyte (fat cell) composed of one large lipid droplet. The most common form of fat in the body. An average adult has 30 billion fat cells with a weight of 30 lbs or 13.5 kg. If excess weight is gained as an adult, fat cells increase in size about fourfold before dividing and increasing the absolute number of fat cells present (Pool 2001).swimming weight loss, but eating too much?
  2. Brown Adipose Tissue (BAT): adipocyte composed of multiple lipid droplets and large amounts of cytoplasm. Brown color is from higher volume of iron-containing mitochondria. Mitochondira are typically found in muscle tissue and produce ATP (energy) while oxidizing fat. Believed to generate heat for the body.

Due to the higher volume of mitochondira, BAT is believed to burn more energy. The presence of BAT in adult’s decreases with age, therefore if one could maintain or increase BAT, one could theoretically burn more energy and calories (allowing one to eat more without the associated weight gain). It is believed certain stimulation with cold submersion is the key to improving BAT, here are a few projected ways to improve BAT:

How to Increase BAT for Swimming Weight Loss

  1. Place an ice pack on the back of the neck or upper back area for 20–30 minutes, preferably in the evening, when insulin sensitivity is lowest. The upper back contains the most BAT.
  2. Consume at least 500 milliliters of ice water on an empty stomach immediately upon waking. In at least two studies, this water consumption has been shown to increase resting metabolic rate 24–30%, peaking at 40–60 minutes post-consumption, though one study demonstrated a lower effect of 4.5% (Ferris 2012).
  3. Take 5–10-minute cold showers before breakfast and/or before bed. Once again focus on the upper back, but be prepared for the surge of energy like taking a shot of espresso! Maintain this position for 1–3 minutes as you acclimate and apply soap to all the necessary regions. Then turn around and rinse normally.
  4. If you’re patient and can tolerate more, take 20-minute baths that induce shivering. This is the most extreme case of BAT stimulation.
  5. Perform fun exercise! One study found performing an enjoyable exercise increases BAT, so have fun with your exercise (Cao 2011).


  1. Bergamin M, Ermolao A, Tolomio S, Berton L, Sergi G, Zaccaria M. Water- versus land-based exercise in elderly subjects: effects on physical performance and body composition. Clin Interv Aging. 2013;8:1109-17. doi: 10.2147/CIA.S44198. Epub 2013 Aug 27 

 Written by Dr. G. John Mullen, DPT, CSCS.