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**Tommy** · January 8, 2004, 06:40 AM

Effect of Protein Intake and Physical Activity on 24-h Pattern and Rate of Macronutrient Utilization

Reference:
Forslund, A.H., El-Khoury, A.E., Olsson, R.M., et al., "Effect of Protein Intake and Physical Activity on 24-h Pattern and Rate of Macronutrient Utilization," American Journal of Physiology, 276(5 Pt1), 1999, pages 964-976.

Summary:

The aim of this study was to evaluate the effect of a high-protein intake compared with a “normal”-protein intake on energy substrate utilization (burning protein, fat or carbohydrate for energy). Fourteen men were placed on a standardized diet and exercise regimen for six days. Then, six of the men were placed in a “high-protein" group, lowering carbohydrate content from 58% to 33% (consuming 2.5 grams of protein per kilogram bodyweight) while eight were placed in a “normal-protein” group (consuming 1 gram of protein per kilogram of bodyweight). All subjects exercised for 90 minutes each day on a stationary bicycle. On days when their blood was tested, subjects engaged in two 90-minute bike workouts. When comparing diets, the high-protein, lower-carbohydrate group used more protein for energy during exercise. However, there was no effect on total 24-hour protein utilization. Subjects on the high-protein diet used more fat for energy during exercise as well as during recovery and at rest, compared with the “normal”-protein group. In addition to burning fat for energy, subjects on the high-protein lower- carbohydrate diet were also in positive nitrogen balance, which prevents the body from breaking down body tissue, such as muscle.

Commentary:
The findings of this study can be applied to the Atkins Principle of Good Health. Consuming a diet higher in protein and lower in carbohydrate while exercising 90 minutes per day, subjects were able to stay in positive nitrogen balance. These subjects also used more fat for energy during exercise, during recovery and at rest than the “normal”-protein group.

http://atkins.com/Archive/2002/1/11-790460.html

**monika** · February 9, 2004, 02:47 PM

thank you tommy, you helped a lot you look really good!! Monika

**Tommy** · February 9, 2004, 02:56 PM

Your welcome Monika. I'm glad it helped. Also thanks for the compliments.

**morein2004** · February 15, 2004, 02:10 PM

I love this kind of stuff. Keep your postings your findings, very encouraging.

**Tommy** · June 25, 2004, 07:42 AM

The truth behind the high protein diet and muscle growth...

High protein diets seem to cause more than their fair share of arguments. And one of the biggest debates centers on how much protein you need to build muscle.

High protein diet
Supporters of a high protein diet point to a series of studies showing that nitrogen balance is increased when you eat more protein.

Nitrogen is found in foods that contain protein (such as fish, meat, poultry, or dairy produce). Nitrogen balance represents the difference between the amount of nitrogen you consume, and the amount of nitrogen you excrete.

If you excrete more nitrogen than you consume, then you're in a negative nitrogen balance. On a high protein diet, you'll consume more nitrogen than you excrete. In this case, nitrogen balance is said to be positive.

Unfortunately, there are several problems with estimating protein needs using nitrogen balance alone. In fact, some researchers believe that people who exercise regularly may actually need less protein.

Let's take a closer look at both sides of the story.

Writing in the International Journal of Sport Nutrition, Dr. Peter Lemon — a researcher specializing in exercise and protein metabolism — concludes that exercise increases your need for protein [4].

Dr. Lemon also points out that your protein needs are likely to be greatest when glycogen levels are low. Glycogen refers to carbohydrate stored in the body.

These findings are nothing new. Back in 1980, Dr. Lemon published research showing that protein is used during exercise to a greater extent than was generally assumed at the time, especially when muscle glycogen levels are low [5].

Lemon estimates that 13.7 grams of protein are used during each hour of aerobic exercise when muscle glycogen is low, compared to 5.8 grams per hour when muscle glycogen is high.

Your body is pretty smart. It can get energy from several different fuel sources. If there's less carbohydrate, your body will burn more fat and protein. And if you don't replace the protein you lose, muscle growth will slow down.

Even moderate intensity aerobic exercise (such as one hour of walking or jogging) increases protein losses [6]. It's not something that affects only people who train with weights.

Exercise at different times of the menstrual cycle also alters protein metabolism. Nine women exercised for 60 minutes at 70% VO2max when estradiol and progesterone were low (menses) and when both were high (in the mid-luteal phase) [3].

Even though diet was the same on both occasions, protein use was greater during the mid-luteal phase. The luteal phase refers to the time between ovulation and the onset of the next menses. It usually lasts between 12 and 16 days.

Nitrogen balance
Many of these studies use nitrogen balance to estimate your protein requirements.

Nitrogen is found in foods that contain protein (such as fish, meat, poultry, or dairy produce). Nitrogen balance represents the difference between the amount of nitrogen you consume, and the amount of nitrogen you excrete.

If you excrete more nitrogen than you consume, then you're in a negative nitrogen balance. If you consume more nitrogen than you excrete, nitrogen balance is said to be positive. If you're trying to gain muscle mass, the goal is not zero balance but to have nitrogen balance as high as possible.

But, there are problems with estimating protein needs using nitrogen balance alone.

For example, let's assume that someone in nitrogen balance starts an exercise program. For the first week or so, nitrogen balance shifts from positive to negative. However, even if protein intake doesn't change, nitrogen balance slowly creeps back to normal [13].

In other words, it's possible to maintain nitrogen balance without eating more protein or making other changes to your diet. And its debatable whether reaching nitrogen balance involves adaptation or accommodation.

The word accommodation refers to the loss of muscle or strength that occurs when your body tries to re-establish a metabolic steady state in response to a drop in protein intake below the required level.

Adaptation, on the other hand, refers to the re-establishment of a metabolic steady state without the loss of muscle or strength.

In one 10-week study, a group of older women was unable to adapt to a low protein diet (just over half of the Recommended Daily Amount). Instead, they accommodated with a loss of muscle, reduced strength and impaired immune responses. But a group of women eating slightly more than the Recommended Daily Amount successfully maintained muscle strength and size [19].

Even older people (aged 55-77 years) given the Recommended Daily Amount of protein for 14 weeks without any exercise accommodated with a drop in muscle size [18].

It's also worth remembering that nitrogen balance improves as your calorie intake increases. In other words, if your protein intake stays constant, but you simply eat more, nitrogen balance will also rise [13].

In short, maintaining nitrogen balance doesn't necessarily mean that protein intake is adequate to support rapid muscle growth. Writing in the August 2003 issue of the British Journal of Nutrition, Professor Joe Millward points out that for most adults eating a diet that meets their calorie requirements, nitrogen balance "ceases to be a useful indicator" of protein requirements [7].

Protein turnover
An increase in dietary protein affects protein turnover in two ways. First, there is an immediate response to the increased intake of protein in meals that consists almost exclusively of a reduction in protein breakdown. Second, there is a long-term adaptation (1–2 weeks) that involves an increase in both protein synthesis and breakdown after a meal.

Your muscles are in a constant state of change. New proteins are being made, while old ones are broken down, or degraded. Skin goes through the same process. Old skin dies off, and your body synthesizes new skin to take its place.

To build muscle, the rate at which proteins are being made has to be greater than the rate at which they're being broken down.

Think of your muscles like a bath. The more water in the bath, the bigger your muscles. Less water in the bath means smaller muscles. For your muscles to grow, there needs to be more water coming into the bath than there is going out.

Water coming into the bath is known as protein synthesis. Water leaving the bath is known as protein breakdown.

For a company to be in profit, for example, income must be greater than expenses. In much the same way, for muscles to grow, protein synthesis must be greater than protein breakdown.

Humans are able to maintain nitrogen balance over a range of dietary protein intakes. This raises the question of not only what is the minimal requirement for protein (your protein needs) but also what is the optimal intake. The nitrogen balance technique gives no information about this optimum. It simply reflects the balance between whole-body protein synthesis and breakdown.

Exercise
A new exercise program might increase your protein need in the short-term. But regular exercise probably doesn't increase protein need at all. In fact, efficiency of nitrogen retention and protein utilization during a program of resistance exercise is higher in older subjects who consume 0.36 vs. 0.70 grams of protein per pound of bodyweight daily [17].

Exercise appears to make your body more efficient in the way it uses protein. In other words, the protein needs of regular exercisers may actually be reduced [16].

However, if you want to lose fat and build muscle, the optimal amount of protein in your diet will probably be increased.

Very few studies have attempted to establish the optimal amount of protein needed for muscle growth. One relevant trial comes from a research group at California State University [23]. The main aim of the study was to establish whether extra protein or simply extra energy would have the biggest impact on muscle growth.

The researchers tracked a group of 73 healthy men for eight weeks. The men were divided into three groups. In addition to their normal diets, group one consumed a high calorie, high protein supplement containing 2,010 calories, 356 grams of carbohydrate and 106 grams of protein.

Group two received a carbohydrate-only supplement containing roughly the same number (2,020) of calories, but less protein (24 grams) and more carbohydrate (450 grams).

The men were told to take one-half of the supplement between the morning and afternoon meal, and the other half before bedtime.

The third group received no supplement and continued with their normal diet. All subjects trained with weights four days each week for 60-90 minutes. Here's a summary of the results.

Group 1

Calories per pound of bodyweight 25.7 calories (4,34

Protein per pound of bodyweight 1.4 grams
Fat-free mass + 6.4 pounds (3.8% of initial weight)
Fat mass + 0.4 pounds

Group 2

Calories per pound of bodyweight 25.9 calories (4,339)
Protein per pound of bodyweight 0.8 grams
Fat-free mass + 7.5 pounds (4.5% of initial weight)
Fat mass - 0.7 pounds

Group 3

Calories per pound of bodyweight 15.0 calories (2,597)
Protein per pound of bodyweight 0.6 grams
Fat-free mass + 3 pounds (1.8% of initial weight)
Fat mass - 1.8 pounds

You can see the impact that extra energy — simply eating more — has on muscle growth. Fat-free mass gains in group one and two were very similar. That's despite the fact that group one were eating almost 50% more protein (1.4 versus 0.8 grams per pound of bodyweight).

Of course, as with all research, this study has limitations.

Firstly, the trial lasted only eight weeks. To see a significant impact of extra protein on muscle growth, it would need to last a lot longer — maybe six months or more. Eight weeks isn't really long enough. Such studies are rare. They're also very costly — in terms of both time and money. And trying to get a large group of people to stick to the same diet and exercise program for more than a few months is very difficult.

It's also worth pointing out that maximal strength in the leg press, bench press and lat pulldown increased by an average of 23% in the high-protein group. In contrast, subjects using the carbohydrate-only supplement were just 14% stronger.

The greater strength gains in the high-protein group do offer limited support for a higher protein intake (1.4 grams per pound of bodyweight) than recommendations based on nitrogen balance data.

Meals
The amount of protein you need in each meal to stimulate the maximum rate of synthesis is still the subject of some debate.

As the level of essential amino acids in the blood rises, protein synthesis goes up. And there's an equally rapid fall as the essential amino acid concentrations begin to decrease. However, protein synthesis drops before amino acid levels return to normal [1, 2, 10, 12].

In one study, infusing amino acids into the blood led to a steep rise in protein synthesis after about 30 minutes. Within two hours, protein synthesis was about four times higher than normal. However, it then started to return to normal despite the fact that amino acids were still being pumped into the blood [2].

In other words, providing your body with more and more protein does not stimulate protein synthesis indefinitely. Excess protein is oxidized (burned to provide energy), used for ureagenesis or converted into sugar. The oversupply of protein also stimulates the activity of enzymes responsible for breaking down amino acids [9].

There's also evidence to show that protein synthesis peaks following the consumption of 20 grams of essential amino acids.

Six grams of essential amino acids stimulates protein synthesis to a greater extent than three grams [20]. But 40 grams has a similar effect as 20 grams [21].

So, while 30 grams of protein might increase protein synthesis to a greater extent than 10 grams of protein, this doesn't mean that 90 grams will be three times better than 30 grams.

In short, eating 5-7 small meals each day, with each meal containing 20-50 grams of protein, is better than 2-3 large meals for anyone wanting more muscle and less fat.

The bottom line
There are still some nutritionists who claim that people who exercise regularly won't benefit from more protein. They insist that the RDA is enough to cover your protein requirements. This advice is so old you'll probably catch it on late night re-runs of Starsky and Hutch.

Using nitrogen balance data, if you're strength training on a regular basis, you'll need to consume roughly 0.8 grams of protein per pound of bodyweight (or 1.7 grams of protein for every kilogram). Endurance athletes need around 0.6 grams per pound of bodyweight (1.4 grams per kilogram).

The problem is that humans are able to maintain nitrogen balance over a range of dietary protein intakes. Nitrogen balance gives no information about optimal intake. It simply reflects the balance between whole-body protein synthesis and breakdown.

One study shows greater strength gains in subjects given more protein (1.4 versus 0.8 grams per pound of bodyweight). But there were no significant differences in muscle growth between the groups.

Although there are concerns that protein leads to kidney damage, even when a diet provides 2.8 grams of protein per kilogram of bodyweight daily (around 1.3 grams per pound), markers of renal function in exercising subjects are within the normal range.

What's more, some researchers estimate that hunter-gatherers (the hunter-gatherer way of life sustained humanity for most of the past 2.4 million years) consumed between 1.2 and 1.7 grams of protein per pound of bodyweight. Protein has formed a safe part of the human diet for many years.

Based on the research we've looked at, the optimal protein intake for muscle growth lies somewhere between 0.8 and 1.4 grams of protein per pound of bodyweight. Most days, I eat between 1.1 and 1.3 grams of protein per pound of bodyweight.

An increase in protein intake does increase your need for fluids, so make sure that any rise in protein consumption is accompanied by an increase in water intake.

Muscle Evo

https://www.thefactsaboutfitness.com

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**rivera11** · December 6, 2004, 09:38 PM

protein

I have a question, I'm female 56 yrs. 5'2' cw 160 lbs. If I drink an 80z. protein shake with a nondairy drink (3 Carbs) a day is this good or not?? I also exercise on the treadmill 40 min. per day 6 days per week. I hope you can help. I'm trying to learn as I go... :help

**Tommy** · December 11, 2004, 03:40 PM

Re: protein

Originally posted by rivera11

I have a question, I'm female 56 yrs. 5'2' cw 160 lbs. If I drink an 80z. protein shake with a nondairy drink (3 Carbs) a day is this good or not?? I also exercise on the treadmill 40 min. per day 6 days per week. I hope you can help. I'm trying to learn as I go... :help

At a 160lbs aim for getting 160 grams of protein per day. It doest say how much protein was in your shake.

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