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Providing clients with nutrition advice can be a critical component of helping them achieve their fitness goals – but only when that advice is founded in fact, writes Matt O’Neill.

Most fitness professionals recognise that attention to diet, as well as to exercise, is vital in order to deliver the results clients need. There are, however, some common nutrition mistakes personal trainers make when advising clients. The following are five of the most frequently observed pitfalls in nutrition advice – and some tips to avoid repeating them with your clients.

1. No dietary accoutability

When you say ‘drop and give me twenty push-ups’, your clients will generally oblige, knowing they will be encouraged and held accountable. Clients use personal trainers to help them stick to their fitness routine. The same needs to apply to dietary training, otherwise you risk frustration for you and your clients when their fitness goals fail to materialise.
Say to your client, ‘I’m helping to hold you accountable for exercise, but you’ll achieve even better results if I can also hold you accountable for your dietary improvements. Can we agree to do this?’ If your client says ‘Yes’ you’ve got a verbal contract on both diet and exercise. Then you can look forward to more rapid progress by better controlling calories-in as well as calories-out.

2. Underdoing carbohydrate

Low-carb, low-energy diets get fast results – but at a cost. Consuming less than around 100 grams of total carbohydrate per day can short-change the body of vital fuel.

The body makes up for the shortfall in carbohydrate by breaking down muscle to create glucose through a process called gluconeogenesis. This strips muscle that is needed to maximise metabolic rate, and increases the likelihood of premature weight loss plateaus and weight regain.

A low-carb diet combined with intense training can also trigger a stress response, elevating cortisol hormone levels, which in turn can trigger cravings and make abdominal fat more resistant to reduction.
You don’t need to go low-carb. Most people simply need to work on limiting carbs, by downsizing portions of bread, pasta, rice and other starchy foods, as well as cutting back on sugary foods.

3. Overdoing protein

Protein is important for muscle maintenance and gains. Although metabolically it’s harder to turn protein into body fat, it’s still possible and excess protein will prevent fat loss. Adding protein shakes and bars to an otherwise adequate-protein diet can make calorie intake too high to see fat loss results.

How many grams of protein does your client consume each day? By finding out this information, you will be able to advise your client on the judiciousness of adding protein supplements to their diet. For body fat reduction, clients should aim for at least one gram per kilogram of body weight per day; for more serious fitness, 1.5 grams is a good guideline; and for muscle gain, an upper limit of two grams should suffice.

At the lower protein target, food will most certainly meet protein needs. At the upper target, some protein supplementation may be required, especially for larger, heavily-muscled individuals.

4. Cutting out food groups

Cutting out a whole food group can cause vitamin or mineral deficiencies and create a less than optimum fat loss diet. The Paleo way of eating eliminates dairy foods, which can leave the individual short on calcium, potentially contributing to osteoporosis. Other popular diets cut starches, fruit or healthy oils without scientific justification, and with the risk of unbalancing a good diet.

The latest research on nutrition for fat loss recognises the important contribution of each food group to an optimum weight management diet.

The following are some minimum exchanges and fat loss benefits from different food groups. This can work as a useful starting checklist when advising clients of daily food intake:

  • 5 serves of vegetables (1 serve = 1 cup salad or ½ cup cooked vegetables) to provide antioxidants that help reduce low-level inflammation associated with insulin resistance and obesity.
  • 2 serves of fruit (1 serve = 1 medium fruit) to also provide antioxidants, fibre for fullness and a natural sweet taste.
  • 2 serves of dairy (200mL milk or 20g slice cheese or 200g tub yoghurt) to provide calcium associated with better fat cell function.
  • 1.5 serves of protein (1 serve = 100g cooked meat or 2 eggs) to provide amino acids for muscle growth, appetite suppression and an increased thermogenic cost of digestion.
  • 3 serves of healthy oils (1 serve = 5g oil or 10g nuts or 1/8 avocado) to optimise cellular function and enhance fat loss, especially when consumed in part from omega-3 fish oils.
  • 3 starches (1 serve = 1 small slice bread or 1 medium potato or ¼ cup muesli) to provide fibre, whole grain antioxidants and slowly digested, low-glycaemic index carbohydrates to balance appetite hormones.

Many fitness enthusiasts will need more exchanges to fuel an active lifestyle, and some people will have adverse reactions to specific foods, like dairy or gluten intolerance. In these instances, it is prudent to refer a client to their GP and a specialist food allergy dietitian for assessment and advice.

5. Supplement surfing

Jumping on each new dietary supplement that hits the market and promoting it to clients is a risky habit, because many just don’t live up to their claims and some can be dangerous. If ‘fat-burner’ pills actually boosted metabolic rate they would need to be reclassified as drugs and placed behind the counter at the pharmacy.
Aside from a multivitamin and fish oil supplements, there are no stand-out supplements for routine recommendation to clients.

Delivering better results

Excellent fat loss, muscle gain and performance results can be achieved with a good fitness program combined with the right total amount and balance of real foods.
The challenge is teaching people how to eat, and to be patient enough to learn the skills to choose, prepare and maintain a healthy diet. It’s not rocket science, but it is food science and that takes some commitment to master. The results are worth it.

Dietitian or nutritionist?

It’s useful to think of a dietitian as a dietary ‘architect’ who is qualified to build a diet that provides the correct balance of nutrients for either general health or to meet specific needs, including those dictated by medical conditions or food intolerances.
While a nutritionist can promote healthy eating, they may not have the expertise to design a diet that is safe and nutritionally optimised for specific results. There are a lot of good nutritionists, but at worst, an unqualified nutritionist is like a dodgy builder who does a renovation job on your diet that could be deemed a health hazard or falls apart in a week or two.

In Australia, to become a nutritionist and use the term Registered Nutritionist, you need to have completed university-level nutrition studies and/or have at least three years’ work experience.

To become a dietitian, you need to complete similar university study, but choose a course that will satisfy membership of the Dietitians Association of Australia (DAA). Members of the DAA can also use the title Accredited Nutritionist.

Useful links:
Nutrition Society of Australia –
Dietitians Association of Australia –


Matt O’Neill, BScMSc (Nut&Diet), APD, AN
Matt is an Accredited Practicing Dietitian and Accredited Nutritionist who appears regularly on the Sunrise and Morning TV shows. His real foods nutrition program has registered over 13,000 people and he trains fitness professionals as Certified Metabolic Jumpstart Coaches. Learn more at

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